The correct answer is C. F’s father.
A and D are brothers. A is a doctor and E is an engineer. E is married to one of the brothers and has two children. B is married to D and G is their child.
Since A and D are brothers, they must have the same parents. Since E is married to one of the brothers, she must be married to either A or D. Since E has two children, one of whom is F, E must be married to A.
Therefore, C is F’s father.
A. A’s son is incorrect because A does not have a son.
B. E’s daughter is incorrect because E does not have a daughter.
D. G’s brother is incorrect because G is a girl and C is a man.