1. 

If A + B ÷ C - D, then A is D's

A. sister
B. grandfather
C. grandmother
D. father
E. None of these

Answer: Option C

Explanation:

Choice (B) and (D) are wrong as A + B means A is a mother, hence a female. Generation gap between A and D is (+1) + (+1) + (0) = 2. So, A must be a grandmother.