B is the sister of A. A is the brother of C. C is the daughter of D. How is B related to D?

Correct — A.
Rule: siblings share parents, and the word sister fixes B as female.

C is the daughter of D, so C is D's child.
A is C's brother and B is A's sister, so A, B and C are siblings.
B is therefore D's child, and female: D's daughter → option (a).

Why the others are wrong

• (b)
  Sister — Sister would put B in D's generation. B is the sister of A and C, who are D's children, so B sits one generation below D.
• (c)
  Son — Son needs a male, and the statement calls B a sister. B is female, so D's child here is a daughter.
• (d)
  Granddaughter — Granddaughter needs two generations between B and D. B is a sibling of D's own child C, so there is one generation, not two.

Four people and three links, but two facts decide it: who shares a generation and what the gender is. B, A and C are siblings, since B is A's sister and A is C's brother.

C is D's daughter, which places the whole sibling group one generation below D. B is female, so B is D's daughter.

Key facts

• The siblings of a person's child are that person's children too.
• Sister and daughter mark a female, brother and son a male.
• A granddaughter is a child's daughter, two generations down.

Common traps

• Answering Sister because B is C's sister, forgetting the question asks about D
• Carrying A's gender (brother) over to B and choosing Son

No directly related past PYQ was found.