Correct : a

Explanation:
1. Analyze the Given Relationships:
• P is the brother of Q: P is Male. P and Q are siblings.
• S is the daughter of Q: S is Female. Q is the parent of S.
• T is the sister of S: T is Female. Both S and T are children of Q.
• R is the mother of Q: R is Female. Since P and Q are siblings, R is the mother of both P and Q.

2. Evaluate Statement (1): R is the grandmother of S.
• R is the mother of Q, and Q is the parent of S. Therefore, R is indeed the grandmother of S. (True)

3. Evaluate Statement (2): P is the uncle of S and T.
• P is the brother of their parent Q, and P is male. Therefore, P is the uncle of both S and T. (True)

4. Evaluate Statement (3): R has only one son.
• We know P is a son of R. However, the gender of Q is not mentioned in the problem (Q could be male or female). We cannot definitively say R has only one son. (False / Cannot be determined)

5. Evaluate Statement (4): Q has only one daughter.
• Both S and T are daughters of Q. Thus, Q has at least two daughters. (False)

6. Conclusion: Since statements (1) and (2) are definitively true, option (a) is the correct choice.