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

Correct — B.
Rule: draw the tree one generation at a time.

B is the husband of C, and D is C's daughter, so D is B's daughter.
A is the father of B, so A is one generation above B and two above D.

A father's father is a grandfather → option (b).

Why the others are wrong

• (a)
  Father — Father is B's relation to D, not A's. A sits one generation higher, as B's father.
• (c)
  Uncle — Uncle would make A a brother of D's father or mother. The stem makes A the father of B, one generation higher than B, not his sibling.
• (d)
  Brother — Brother puts A in D's own generation. A is B's father and B is D's father, so A is two generations above D.

Blood-relation items reward a quick tree: couples on one line, children one line below. Mark each person's generation and, where it matters, gender.

Here A is at the top, B and his wife C one step down, and D one step below them. A is male (a father) and two generations above D, which makes him D's grandfather, on the father's side.

Key facts

• Father's father = paternal grandfather.
• Mother's father = maternal grandfather.
• A man two generations above you in a direct line is your grandfather.

Common traps

• Answering Father, which is B's relation to D, not A's
• Missing that D is B's daughter because the stem links D to C instead of B

No directly related past PYQ was found.