‘A # B’ means ‘A is the daughter B’
‘A @ B’ means ‘A is the only son of B’.
‘A & B’ means ‘A is the mother of B’.
‘A % B’ means ‘A is the father-in-law of B’.

If P # Q @ R % S & T @ Q, then how is P related to T?

Let's decode the expression step by step:
T @ Q: T is the only son of Q.

S & T: S is the mother of T.

Since T is the son of both Q and S, Q (father) and S (mother) are a married couple.

R % S: R is the father-in-law of S.

Since S is married to Q, R is the father of Q.

Q @ R: Q is the only son of R (consistent with the above deduction).

P # Q: P is the daughter of Q.

Now, let's look at the relationship between P and T:

Both P and T are children of the couple Q and S.

T is a male (son) and P is a female (daughter).

Therefore, P is the Sister of T.

Hence, the correct option is A.