Today’s question of the day gives you a chance to practice your data sufficiency skills. Click here for the answer and explanation.

Explanation:

Note that we cannot be sure that y = z since x may be 0. So we are left with two possibilities

x = 0 or y = z.

Statement (1)

We still don’t know whether x is 0. So, if x is 0, then z may or may not be equal to 4. If x ≠ 0, z = y = 2. This statement alone is insufficient.

The correct answer would be among B/C/E.

Statement (2)

x is a positive integer means that x ≠ 0 and y = z. However, we don`t know the value of either y or z. This statement alone is insufficient.

The correct answer would be between C/E.

Statement (1 & 2)

From statement (2), we know that x ≠ 0 and y = z, and from statement (1), we know that y = 2; hence, we know that z = 2 ≠ 4, a unique answer.

Correct choice is C.