Correct option is C
Given - In a certain code language,
A + B means 'A is the wife of B',
A-B means 'A is the father of B',
A x B means 'A is the brother of B' and
A ÷ B means 'A is the sister of B'.

F ÷ L × C + A - S

F is mother’s sister of S.
option c is correct.