In a certain code language,
A + B means 'A is the mother of B'
A - B means 'A is the brother of B'
A × B means 'A is the wife of B'
A ÷ B means 'A is the father of B'
Based on the above, how is S related to U if 'Q × R - S ÷ T + U'?
1
Daughter
2
Brother's wife
3
Mother's father
4
Mother's husband