Practice GMAT Data Sufficiency Question

If X is a positive integer, is X a prime number?

A)	Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
B)	Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
C)	BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
D)	EACH statement ALONE is sufficient.
E)	Statement (1) and (2) TOGETHER are NOT sufficient to answer the question asked, and additional data are needed.

Correct Answer: B

Evaluate Statement (1) alone.
1. Make a list of even numbers and evaluate whether they are prime:
  2: Prime
  4: Not Prime
  6: Not Prime
  8: Not Prime
  10: Not Prime
2. Every single even number except 2 is not a prime number. However, since Statement (1) enables X to be prime (e.g., 2) and not prime (e.g., 4, 6, 8, 10, …), Statement (1) is NOT SUFFICIENT.
3. Statement (1) alone is NOT SUFFICIENT.
Evaluate Statement (2) alone.
1. List the possible values of X, remembering that X is a positive integer such that 1 < X < 4:
  X = 2: Prime Number
  X = 3: Prime Number
  Since all possible values of X given the parameters in Statement (2) are prime, Statement (2) is SUFFICIENT.
2. Statement (2) alone is SUFFICIENT.
Since Statement (1) alone is NOT SUFFICIENT and Statement (2) alone is SUFFICIENT, answer B is correct.