|A) Lawyer||B) Teacher|
|C) Doctor||D) None of these|
C is the daughter-in-law of A who is the grandmother of F means C is the mother of F But F is the son of B.
So. B is C's husband. But C, the lawyer. is married to the Doctor So. B is the Doctor. F. the Accountant, will he the non of B and C E is the unmarried Engineer
So. the other married couple can be that of grandmother of F. i.e, A and D. But D, the Salesman, is married to the Lady Teacher.
So. D, the Salesman, is the grandfather of F. father of B and the husband of A. the Lady Teacher.
A is the Lady Teacher