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?
I. M - N x C + F
II. F - C + N x M
III. N + M - F x C
IV. M x N - C + F

Question: 以下哪项是正确的？
Options:
A. II 或 I, B. III 或 I, C. IV 或 I, D. I 或 II, E. 仅 I
Answer: C
True statement: IV