Correct
Explanation
A and B are brothers and C is B's father, so A is C's son. Now, D is C's father, so A is D's grandson.
Solve this puzzle
Which Christmassy song plays at the end of the 1988 film Die Hard?
'I'll Be Home For Christmas' 'Let It Snow! Let It Snow! Let It Snow!' 'White Christmas' 'Have Yourself a Merry Little Christmas'