'A+B' means 'A is the brother of B', 'A×B' means 'A is the mother of B', 'A-B' means 'A is the wife of B', 'A÷B' means 'A is the father of B'.

If P+Q×R÷S-T; how is 'Q' related to 'T'?

Given: 'A+B' means 'A is the brother of B',

'A×B' means 'A is the mother of B',

'A-B' means 'A is the wife of B',

'A÷B' means 'A is the father of B'.

If P+Q×R÷S-T;

'Q' related to 'T' as ​Wife's Grand-mother.

Thus, correct option is (a).