If A + B means A is the brother of B; A – B means A is the sister of B and A x B means A is the father of B. Which of the following means that C is the son of M?

The correct answer is D.

A. M – N x C + F
This means that M is the brother of N, who is the father of C. This is not possible, since a brother cannot be the father of his sibling.

B. F – C + N x M
This means that F is the sister of C, who is the father of N. This is also not possible, since a sister cannot be the father of her sibling.

C. N + M – F x C
This means that N is the father of M, who is the brother of C. This is not possible, since a father cannot be the brother of his child.

D. M x N – C + F
This means that M is the father of N, who is the son of C. This is possible, since a father can be the son of his own child. Therefore, the answer is D.