A is the daughter of B. B is the son of C. C is the father of D. How is A related to D?

Correct — B.
Rule: place everyone by generation, then read A's link to D.

C is the father of both B and D, so B and D are siblings.
A is B's daughter, one generation below them.

A sibling's daughter is a niece → option (b).

Why the others are wrong

• (a)
  Sister — A sister of D would be another child of C, level with B and D. A is B's daughter, a generation below D.
• (c)
  Granddaughter — A is C's granddaughter, through B. D is C's child, on B's level, so D is A's uncle or aunt, not a grandparent.
• (d)
  Cousin — A and D would be cousins only if their parents were siblings. D's parent is C, A's grandfather, so D is A's uncle or aunt.

Blood-relation chains are solved with a small family tree: one row per generation, a line from each parent to each child.

Here C sits at the top, B and D below him as his children, and A below B. Two people who share a parent are siblings, and a sibling's child is a nephew or niece.

The word daughter fixes A as female, so A is D's niece.

Key facts

• Two children of the same father are siblings: here B and D.
• A sibling's daughter is a niece, whatever the sibling's sex.
• A is C's granddaughter, but the question asks about D.

Common traps

• Answering A's relation to C (granddaughter) when the question asks about D
• Reading the question backwards and naming D's relation to A (uncle or aunt)

No directly related past PYQ was found.