Correct option is B
Given - M is the daughter of R. Z is the husband of M. X is the son of R. Z is the son-in-law of Y

1. M is the daughter of R.
2. Z is the husband of M.
3. X is the son of R.
4. Z is the son-in-law of Y.

From the above family diagram X is son of Y.
Correct answer is (b) Son