If A is the sister of B, C is the daughter of A, D is the sister of A and E is the brother of C. How is D related to E?
Mother’s sister
The correct answer is option 3 i.e. Mother’s sister.

(In above diagram, circle represents female, square represents male, single line means siblings, vertical line shows generational gap.)
So, D is the 'Mother’s sister' of E.
Select the most appropriate option to improve the bold part of the sentence.
The manager discussed on the issue in detail.