(1) m > a

(2) a + b + c + d = 0

Solution:

s will be zero only in two instances: (i) when all the elements in the set are the same, or (ii) the set contains only one element, which in this case is not possible. So, we need to check whether a, b, c, and d are the same integers.

Statement (1): m > a

The average will be equal to a, b, c, and d only when a = b = c = d. Since m > a, all the elements in the set cannot be the same, and therefore, s > 0.

SUFFICIENT

Statement (2): a + b + c + d = 0

When a = b = c = d = 0, s = 0

When a = -4, b = 0, c = 0, and d = 4, s > 0

NOT sufficient

Answer: A

Labels: GMAT CAT Test, GMAT Data Sufficiency, GMAT Descriptive Statistics, GMAT DS, GMAT Standard Deviation, GMAT Tough Math Questions