Which of the following is the code for 'elders'

What does the code 'za' stand for 

Which of the following is the code for 'must'

If P+Q means Q is mother of P, P × C means Q is the son of P, P-Q means Q is the daughter of P, and P ÷ Q means Q is the husband of P, then which of the following shows K is grandmother of N

If B-C means B is father of C,B+C means B is brother of C, B ÷ C means B is mother of C, and B × C means B is wife of C, then which of the following represents the relationship 'A is grandmother of D'

If P + Q means P is mother of Q, P-Q means P is sister of Q and P × Q means P is brother of Q. Which of the following represents D is nephew of A