|A) CD||B) DE|
|C) EB||D) none of these|
C is wife of B. So, one couple is BC. Now, D in grandmother of A, B is the son of D and his wife C is the mother of F. SO, D is also the grandmother of F But F is the granddaughter of E.
So, E is the grandfather of F and the husband of D. Thus, DF is another couple