GATE 2017 Computer Science and Information Technology Session 1
Q. 1 The statement (¬p) ⇒ (¬q) is logically equivalent to which of the statements below?
I. p ⇒ q
II. q ⇒ p
III. (¬q) ∨ p
IV. (¬p) ∨ q
A. I only
B. I and IV only
C. II only
D. II and III only
Q. 2 Consider the first-order logic sentence F : ∀x (∃y R(x, y)). Assuming non-empty logical domains, which of the sentences below are implied by F?
I. ∃y (∃x R(x, y))
II. ∃y (∀x R(x, y))
III. ∀y (∃x R(x, y))
IV. ¬∃x (∀y ¬R(x, y))
A. IV only
B. I and IV only
C. II only
D. II and III only
Q. 3 Let c_1, …, c_n be scalars, not all zero, such that for i = 0 to n, Σ c_i a_i = 0 where a_i are column vectors in R^n. Consider the set of linear equations Ax = b where A = [a_1 , … , a_n] and b = Σ a_i for i = 1 to n. The set of equations has
A. a unique solution at x = J_n where J_n denotes an n-dimensional vector of all 1
B. no solution
C. infinitely many solutions
D. finitely many solutions
Q. 4 Consider the following functions from positive integers to real numbers:
10, √n, n, log2 n, 100/n.
The CORRECT arrangement of the above functions in increasing order of asymptotic complexity is
A. log2 n, 100/n, 10, √n, n
B. 100/n, 10, log2 n, √n, n
C. 10, 100/n, √n, log2 n, n
D. 100/n, log2 n, 10, √n, n
Q. 5 Consider the given table. Match the algorithms to the design paradigms they are based on.
A. (P) ↔ (ii); (Q) ↔ (iii); (R) ↔ (i)
B. (P) ↔ (iii); (Q) ↔ (i); (R) ↔ (ii)
C. (P) ↔ (ii); (Q) ↔ (i); (R) ↔ (iii)
D. (P) ↔ (i); (Q) ↔ (ii); (R) ↔ (iii)
Q. 6 Let T be a binary search tree with 15 nodes. The minimum and maximum possible heights of T are:
**The height of a tree with a single node is 0.
A. 4 and 15 respectively.
B. 3 and 14 respectively.
C. 4 and 14 respectively.
D. 3 and 15 respectively.
Q. 7 The n-bit fixed-point representation of an unsigned real number X uses f bits for the
fraction part. Let i = n – f. The range of decimal values for X in this representation is
A. 2^(-f) to 2^i
B. 2^(-f) to [2^i – 2^(-f)]
C. 0 to 2^i
D. 0 to [2^i – 2^(-f)]
Question 8
typedef struct node {
int data;
node *next;
} node;
void join (node *m, node *n) {
node *p = n;
while (p -> next != NULL) {
p = p -> next;
}
p -> next = m;
}
Q. 8 Consider the given C code fragment. Assuming that m and m point to valid NULLterminated linked lists, invocation of join will
A. append list m to the end of list n for all inputs.
B. either cause a null pointer dereference or append list m to the end of list n.
C. cause a null pointer dereference for all inputs.
D. append list n to the end of list m for all inputs.
Q. 9 When two 8-bit numbers A_7 … A_0 and B_7 … B_0 in 2’s complement representation (with A_0 and B_0 as the least significant bits) are added using a ripple-carry adder, the sum bits obtained are S_7 … S_0 and the carry bits are C_7 … C_0. An overflow is said to have occurred if
A. the carry bit C_7 is 1
B. all the carry bits (C_7, …, C_0) are 1
C. (A_7 . B_7 . (S_7)’ + (A_7)’ . (B_7)’ . S_7) is 1
D. (A_0 . B_0 . (S_0)’ + (A_0)’ . (B_0)’ . S_0) is 1
Q. 10 Consider the following context-free grammar over the alphabet Σ = {a, b, c} with S as the start symbol:
S → abScT | abcT
T → bT | b
Which one of the following represents the language generated by the above grammar?
A. {(ab)^n (cb)^n | n ≥ 1}
B. {(ab)^n (cb)^m1 (cb)^m2 … (cb)^mn | n, m1, m2, … , mn ≥ 1}
C. {(ab)^n ((cb)^m)^n | m, n ≥ 1}
D. {(ab)^n ((cb)^n)^m | m, n ≥ 1}
Question 11
struct data {
int marks[100];
char grade;
int cnumber;
};
struct data student;
Q. 11 Consider the given C struct. The base address of student is available in register R1. The field student.grade can be accessed efficiently using
A. Post-increment addressing mode, (R1)+
B. Pre-decrement addressing mode, -(R1)
C. Register direct addressing mode, R1
D. Index addressing mode, X(R1), where X is an offset represented in 2’s complement 16- bit representation.
Q. 12 Consider the following intermediate program in three-address code:
p = a – b
q = p * c
p = u * v
q = p + q
Which one of the following corresponds to a static single assignment form of the above code?
A. p1 = a – b q1 = p1 * c p1 = u * v q1 = p1 + q1
B. p3 = a – b q4 = p3 * c p4 = u * v q5 = p4 + q4
C. p1 = a – b q1 = p2 * c p3 = u * v q2 = p4 + q3
D. p1 = a – b q1 = p * c p2 = u * v q2 = p + q
Question 13
#include
int *assignval (int *x, int val) {
*x = val;
return x;
}
void main() {
int *x = malloc (sizeof(int));
if (NULL == x) return;
x = assignval (x, 0);
if (x) {
x = (int *) malloc (sizeof(int));
if (NULL == x) return 0;
x = assignval (x, 10);
}
printf (“%d\n”, *x);
free (x);
}
Q. 13 Consider the given C code. The code suffers from which one of the following problems?
A. compiler error as the return of malloc is not typecast appripriately
B. compiler error because the comparison should be made as x == NULL and not as shown
C. compiles successfully but execution may result in dangling pointer
D. compiles successfully but execution may result in memory leak
Q. 14 Consider a TCP client and a TCP server running on two different machines. After completing data transfer, the TCP client calls close to terminate the connection and a FIN segment is sent to the TCP server. Server-side TCP responds by sending an ACK, which is received by the client-side TCP. As per the TCP connection state diagram (RFC 793), in which state does the client-side TCP connection wait for the FIN from the server-side TCP?
A. LAST-ACK
B. TIME-WAIT
C. FIN-WAIT-1
D. FIN-WAIT-2
Q. 15 A sender sends a message m to receiver R, which is digitally signed by S with its private key. In the scenario, one or more of the following security violations take place:
(I) S can launch a birthday attack to replace m with a fraudulent message.
(II) A third party attacker can launch a birthday attack to replace m with a fraudulent message.
(III) R can launch a birthday attack to replace m with a fraudulent message.
Which one of the following are possible security violations?
A. (I) and (II) only
B. (I) only
C. (II) only
D. (II) and (III) only
Q. 16 The following functional dependencies hold true for the relational schema R {V, W, X, Y, Z}:
V → W
VW → X
Y → VX
Y → Z
Which of the following is irreducible equivalent for this set of functional dependencies?
A. V → W V → X Y → V Y → Z
B. V → W W → X Y → V Y → Z
C. V → W V → X Y → V Y → X Y → Z
D. V → W W → X Y → V Y → X Y → Z
Q. 17 Consider the following grammar:
P → xQRS
Q → yz | z
R → w | ε
S → y
What is FOLLOW(Q)?
A. {R}
B. {w}
C. {w, y}
D. {w, $}
Q. 18 Threads of a process share
A. global variables but not heap.
B. heap but not global variables.
C. neither global variables nor heap.
D. both heap global variables.
Q. 19 Let X be a Gaussian random variable with mean 0 and variance σ². Let Y = max(X, 0) where max(a, b) is the maximum of a and b. The median of Y is
Q. 20 Let T be a tree with 10 vertices. The sum of the degrees of all vertices in T is __________.
Q. 21 Consider the given Karnaugh map, where X represents “don’t care” and blank represents 0. Assume for all inputs (a, b, c, d), the respective complements (a’, b’, c’, d’) are also available. The given logic is implemented using 2-input NOR gates only. The minimum number of gates required is _______.
Q. 22 Consider the language L given by the regular expression (a + b)* b (a + b) over the alphabet {a, b}. The smallest number of states needed in a deterministic finite-state automaton (DFA) accepting L is __________.
Q. 23 Consider a database that has the relation schema EMP (EmpId, EmpName and DeptName). An instance of the schema EMP and an SQL query on it are given. The output of executing the SQL query is ________.
Q. 24 Consider the given CPU processes with arrival times (in milliseconds) and length of CPU bursts (in milliseconds) as given in the table. If the preemptive shortest remaining time first scheduling algorithm is used to schedule the processes, then the average waiting time across all processes is ___________ milliseconds.
Q. 25 Consider a two-level cache hierarchy with L1 and L2 caches. An application incurs 1.4 memory accesses per instruction on average. For this application, the miss rate of L1 cache is 0.1; the L2 cache experiences, on average, 7 misses per 1000 instructions. The miss rate of L2 expressed correct to two decimal places is ____________.
Q. 26 Let G = (V, E) be any connected undirected edge-weighted graph. The weights of the edged in E are positive and distinct. Consider the following statements:
(I) Minimum Spanning Tree of G is always unique.
(II) Shortest path between any two vertices of G is always unique.
Which of the above statements is/are necessarily true?
A. (I) only
B. (II) only
C. both (I) and (II)
D. neither (I) nor (II)
Q. 27 A multithreaded program P executes with x number of threads and uses y number of locks for ensuring mutual exclusion while operating on shared memory locations. All locks in the program are non-reentrant, i.e., if a lock holds a lock l, then it cannot re-acquire lock l without releasing it. If a thread is unable to acquire a lock, it blocks until a lock becomes available. The minimum value of x and the minimum value of y together for which execution of P can result in a deadlock are
A. x = 1, y = 2
B. x = 2, y = 1
C. x = 2, y = 2
D. x = 1, y = 1
Q. 28 The value of lim_(x→1) (x^7 – 2x^5 + 1) / (x^3 – 3x^2 + 2)
A. is 0
B. is -1
C. is 1
D. does not exist
Q. 29 Let p, q, and r be propositions and the expression (p → q) → r be a contradiction. Then, the expression (r → p) → q is
A. a tautology.
B. a contradiction.
C. always TRUE when p is FALSE.
D. always TRUE when q is TRUE.
Q. 30 Let u and v be two vectors in R² whose Euclidean norms satisfy ||u|| = 2 ||v||. What is the value of α such that w = u + αv bisects the angle between u and v?
A. 2
B. 1/2
C. 1
D. -1/2
Q. 31 Let A be n X n real valued square symmetric matrix of rank 2 with Σ_(i = 1 to n) Σ_(j = 1 to n)
(A_ij)² = 50. Consider the following statements:-
(I) One eigenvalue must be in [-5, 5].
(II) The eigenvalue with largest magnitude must be strictly greater than 5.
Which of the above statements about eigenvalues of A is/are necessarily CORRECT?
A. Both (I) and (II)
B. (I) only
C. (II) only
D. Neither (I) nor (II)
Q. 32 A computer network uses polynomials over GF(2) for error checking with 8 bits as
information bits and uses x³ + x + 1 as the generator polynomial to generate the check bits. In this network, the message 01011011 is transmitted as
A. 01011011010
B. 01011011011
C. 01011011101
D. 01011011100
Q. 33 Consider a combination of T and D flip-flops connected as shown in the figure. The output of the D flip-flop is connected to the T flip-flop and the output of the T flip-flop is connected to the input of the D flip-flop. Initially, both Q0 and Q1 are set to 1 (before the 1st clock cycle). The outputs
A. Q1Q0 after the 3rd cycle are 11 and after the 4th cycle are 00 respectively
B. Q1Q0 after the 3rd cycle are 11 and after the 4th cycle are 01 respectively
C. Q1Q0 after the 3rd cycle are 00 and after the 4th cycle are 11 respectively
D. Q1Q0 after the 3rd cycle are 01 and after the 4th cycle are 01 respectively
Q. 34 If G is a grammar with productions S → SaS | aSb | bSa | SS | ∈ where S is the start variable. Then which one of the following strings is not generated by G?
A. abab
B. aaab
C. abbaa
D. babba
Question 35
void fun1 (int n) {
if (n == 0) return;
printf (“%d”, n);
fun2 (n – 2);
printf(“%d”, n);
}
void fun2 (int n) {
if (n == 0) return;
printf (“%d”, n);
fun2 (++n);
printf(“%d”, n);
}
Q. 35 Consider the given two functions. The output printed when fun1(5) is called is
A. 53423122233445
B. 53423120112233
C. 53423122132435
D. 53423120213243
Question 36
int foo (int val) {
int x = 0;
while (val > 0) {
x = x + foo (val – -);
}
return val;
}
int bar (int val) {
int x = 0;
while (val > 0) {
x = x + bar (val – -);
}
return val;
}
Q. 36 Consider the C functions foo and bar as given. Invocations of foo(3) and bar(3) will result in:
A. Return of 6 and 6 respectively.
B. Infinite loop and abnormal termination respectively.
C. Abnormal termination and infinite loop respectively.
D. Both terminating abnormally.
Q. 37 Consider the context-free grammars over the alphabet {a, b, c} given below. S and T are non-terminals.
G1 : S → aSb | T, T → cT | ∈
G2 : S → bSa | T, T → cT | ∈
The language L(G1) ∩ L(G2) is
A. Finite.
B. Not finite but regular.
C. Context-free but not regular.
D. Recursive but not context-free.
Q. 38 Consider the languages L1 and L2 over the alphabet Σ = {a, b, c}. Let L1 = {a^n b^n c^m | m, n ≥ 0} and L2 = {a^m b^n c^n | m, n ≥ 0}. Which of the following are context-free languages?
I. L1 ∪ L2
II. L1 ∩ L2
A. I only
B. II only
C. I and II
D. Neither I nor II
Q. 39 Let A and B be finite alphabets and let # be a symbol outside both A and B. Let f be a total function from A* to B*. We say f is computable if there exits a Turing machine M which, given an input x in A*, always halts with f(x) on its tape. Let Lf denote the language {x # f(x) | x ∈ A*}. Which of the following statements is true?
A. f is computable if and only if Lf is recursive.
B. f is computable if and only if Lf is recursively enumerable.
C. If f is computable then Lf is recursive, but not conversely.
D. If f is computable then Lf is recursively enumerable, but not conversely.
Q. 40 Recall that Belady’s anomaly is that the page-fault rate may increase as the number of allocated frames increases. Now, consider the following statements:
S1 : Random page replacement algorithm (where a page chosen at random is replaced)
suffers from Belady’s anomaly
S2 : LRU page replacement algorithm suffers from Belady’s anomaly
Which of the following is CORRECT?
A. S1 is true. S2 is true.
B. S1 is true. S2 is false.
C. S1 is false. S2 is true.
D. S1 is false. S2 is false.
Q. 41 Consider a database that has the relation schemas EMP (EmpId, EmpName, DeptId) and DEPT (DeptName, DeptId). Note that the DeptId can be permitted to be NULL in the relation EMP. Consider the following queries on the database expressed in tuple relational calculus.
(I) { t | ∃u ∈ EMP( t{EmpName] = u[EmpName] ∧ ∀ v ∈ DEPT( t[DeptId] ≠ v[DeptId] ))}
(II) { t | ∃u ∈ EMP( t{EmpName] = u[EmpName] ∧ ∃ v ∈ DEPT( t[DeptId] ≠ v[DeptId] ))}
(III) { t | ∃u ∈ EMP( t{EmpName] = u[EmpName] ∧ ∃ v ∈ DEPT( t[DeptId] = v[DeptId] ))}
Which of the above queries are safe?
A. (I) and (II) only
B. (I) and (III) only
C. (II) and (III) only
D. (I), (II) and (III)
Q. 42 In a database system, unique timestamps are assigned to each transaction using Lamport’s logical clock. Let TS(T1) and TS(T2) be the timestamps of transactions T1 and T2, respectively. Besides, T1 holds a lock on the resource R, and T2 has requested a conflicting lock on the same resource R. The following algorithm is used to prevent deadlocks in the database system assuming that a killed transaction is restarted with the same timestamp.
if TS(T2) < TS(T1) then
T1 is killed
else T2 waits.
Assume any transaction that is not killed terminates eventually. Which of the following is TRUE about the database system that uses the above algorithm to prevent deadlocks?
A. The database system is both deadlock-free and starvation-free.
B. The database system is deadlock-free, but not starvation-free.
C. The database system is starvation-free, but not deadlock-free.
D. The database system is neither deadlock-free nor starvation-free.
Question 43
stmt → if expr then expr else expr ; stmt | ∅
expr → term relop term | term
term → id | number
id → a | b | c
number → [0 – 9]
where relop is a relational operator (e.g., <, >, …), ∅ refers to the empty statement,
and if, then, else are terminals.
Q. 43 Consider the given grammar. Consider a program P following the given grammar
containing ten if terminals. The number if control flow paths in P is _______.
For example, the program
if e1 then e2 else e3
has 2 control flow paths, e1 → e2 and e1 → e3.
Q. 44 In an RSA cryptosystem, a participant A uses two prime numbers p=13 and q=17 to generate her public and private keys. If the public key of A is 35, then the private key of A is ________.
Q. 45 The values of parameters for the Stop-and-Wait ARQ protocol are as given below:
Bit rate of the transmission channel = 1 Mbps Propagation delay from sender to receiver = 0.75 ms Time to process a frame = 0.25 ms
Number of bytes in the information frame = 1980
Number of bytes in the acknowledge frame = 20
Number of overhead bytes in the information frame = 20
Assume that there are no transmission errors. Then, the transmission efficiency
(expressed in percentage) of the Stop-and-Wait ARQ protocol for the above parameters is __________ (correct to 2 decimal places).
Q. 46 Consider a database that has the relation schema CR (StudentName, CourseName). An instance of the schema CR is as given in the figure. The following query is made on the database.
T1 ← Π_(CourseName) (σ_(StudentName=’SA’) (CR))
T2 ← CR ÷ T1
The number of rows in T2 is
Q. 47 The number of integer between 1 and 500 (both inclusive) that are divisible by 3 or 5 or 7:
Q. 48 Let A be an array of 31 numbers consisting of a sequence of 0’s followed by a sequence of 1’s. The problem is to find the smallest index i such that A[ i ] is 1 by probing the minimum number of locations in A. The worst case number of probes performed by an optimal algorithm is _______.
Q. 49 Consider an RISC machine where each instruction is exactly 4 bytes long. Conditional and unconditional branch instructions use PC-relative addressing mode with Offset specified in bytes to the target location of the branch instruction. Further the Offset is always with respect to the address of the next instruction in the program sequence. Consider the given instruction sequence. If the target of the branch instruction is i, then the decimal value of the Offset is ________.
Q. 50 Instruction execution in a processor is divided into 5 stages, Instruction Fetch (IF),
instruction Decode (ID), Operand Fetch (OF), Execute (EX), and Write Back (WB). These stages take 5, 4, 20, 10, and 3 nanoseconds (ns) respectively. A pipelined implementation of the processor requires buffering between each pair of consecutive stages with a delay of 2 ns. Two pipelined implementations of the processor are contemplated:
(i) a naive pipeline implementation (NP) with 5 stages and
(ii) and efficient pipeline (EP) where the OF stage is divided into stages OF1 and OF2 with execution times of 12 ns and 8 ns, respectively.
The speedup (correct up to 2 decimal places) achieved by EP over NP in executing 20
independent instructions with no hazards is _________.
Q. 51 Consider a 2-way set associative cache with 256 blocks and uses LRU replacement. Initially the cache is empty. Conflict misses are those misses which occur due to connection of multiple blocks for the same cache set. Compulsory misses occur due to first time access to the block. The sequence of access to memory blocks (0, 128, 256, 128, 0, 128, 256, 128, 1, 129, 257, 129, 1, 129, 257, 129) is repeated 10 times. The number of conflict misses experienced by the cache is _________.
Q. 52 Consider the expression (a – 1)* (((b + c) / 3) + d)). Let X be the minimum number of registers required by an optimal code generation (without any register spill) algorithm for a load/store architecture, in which (i) only load ans store instructions can have memory operands and (ii) arithmetic instructions can have only register or immediate operands. The value of X is __________.
Question 53
#include
#include
void printlength (char *s, char *t) {
unsigned int c = 0;
int len = ((strlen(s) strlen(t)) > c) ? strlen(s) : strlen(t);
printf(“%d”, len);
}
void main() {
char *x = “abc”;
char *y = “defgh”;
printlength(x, y);
}
Q. 53 Consider the given C program. Recall that strlen is defined in string.h as returning a value of type size_t, which is and unsigned int. The output of the program is ____________.
Q. 54 A cache memory unit with capacity of N words and block size of B words is to be designed. If it is designed as a direct mapped cache, the length of the TAG field is 10 bits. If the cache unit is now designed as a 16-way set-associative cache, the length of the TAG field is _______ bits.
Question 55
#include
int total (int v) {
static int count = 0;
while (v) {
count += v & 1;
v >>= 1;
}
return count;
}
void main() {
static int x = 0;
int i = 5;
for( ; i > 0; i – -) {
x = x + total (i);
}
printf(“%d\n”, x);
}
Q. 55 The output of the given C program is _________.
Q. 56 After Rajendra Chola returned from his voyage to Indonesia, he ________ to visit the temple in Thanjavur.
A. was wishing
B. is wishing
C. wished
D. had wished
Q. 57 Research in the workplace reveals that people work for many reasons ________.
A. money beside
B. beside money
C. money besides
D. besides money
Q. 58 Rahul, Murali, Srinivas and Arul are seated around a square table. Rahul is sitting to the left of Murali. Srinivas is sitting to the right of Arul. Which of the following pairs are seated opposite each other?
A. Rahul and Murali
B. Srinivas and Arul
C. Srinivas and Murali
D. Srinivas and Rahul
Q. 59 Find the smallest number y such that y × 162 is a perfect cube.
A. 24
B. 27
C. 32
D. 36
Q. 60 The probability that a k-digit number does NOT contain the digits 0, 5, or 9 is
A. 0.3^k
B. 0.6^k
C. 0.7^k
D. 0.9^k
Q. 61 “The hold of the nationalist imagination on our colonial past is such that anything
inadequately or improperly nationalist is not just history.” Which of the following statements best reflects the author’s opinion?
A. Nationalists are highly imaginative.
B. History is viewed through the filter of nationalism.
C. Our colonial past never happened.
D. Nationalism has to be both adequately and properly imagined.
Q. 62 Six people are seated around a circular table. There are at least two men and two women. There are at least three right-handed persons. Every woman has a left-handed person to her immediate right. None of the women are right-handed. The number of women at the table is
A. 2
B. 3
C. 4
D. Cannot be determined
Q. 63 The expression [ (x – y) – |x – y| ] / 2 is equal to
A. the maximum of x and y
B. the minimum of x and y
C. 1
D. none of the above
Q. 64 Arun, Gulab, Neel and Shweta must choose one shirt each from a pile of four shirts coloured red, pink, blue and white, respectively. Arun dislikes the colour red ans Shweta dislikes the colour white. Gulab and Neel like all the colours. In how many different ways can they choose the shirts so that no one has a shirt with a colour he or she dislikes?
A. 21
B. 18
C. 16
D. 14
Q. 65 A contour line joins locations having the same height above the mean sea level. A contour plot of a geographical region is given. Contour lines are shown at 25 m intervals in this plot. If in a flood, the water level rises to 525 m, which of the villages P, Q, R, S, T get submerged?
A. P, Q
B. P, Q, T
C. R, S, T
D. Q, R, S
| Answer Sheet |
||||||||||
| Question | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
| Answer | D | B | C | B | C | B | D | B | C | B |
| Question | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 |
| Answer | D | B | D | D | B | A | C | D | 0 | 18 |
| Question | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 |
| Answer | 1 | 4 | 2.6 | 3 | 0.05 | A | D | C | D | A |
| Question | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 |
| Answer | B | C | B | D | A | C | B | A | A | B |
| Question | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50 |
| Answer | D | A | 1024 | 11 | 86.5 To 89.5 | 4 | 271 | 5 | 2 | 1.49 To 1.52 |
| Question | 51 | 52 | 53 | 54 | 55 | 56 | 57 | 58 | 59 | 60 |
| Answer | 76 | 2 | 3 | 14 | 23 | C | D | C | D | C |
| Question | 61 | 62 | 63 | 64 | 65 | |||||
| Answer | B | A | B | D | C |