If 'A $ B' means 'A is the father of B', 'A B' means 'A is the mother of B', 'A @ B' means 'A is the wife of B', then which of the following means 'M is the grandmother of N' ?

Question

( A ) M R @ T @ N
( B ) M T $ N @ R
( C ) M T $ R @ S
( D ) M R $ T @ N