P is the brother of Q and R. S is R's mother. T is P's father. How many of the following statements are definitely true ? I. S and T are a couple. II. Q is T's son. III. T is Q's father. IV. S is P's mother. V. R is T's daughter. VI. P is S's son. Select the correct answer using the code given below :

(a) Only two
(b) Only three
(c) Only four ✓ UPSC's answer
(d) Only five

Why the answer is (c)

• P is the brother of Q and R, meaning P, Q, and R are siblings with the same parents.

• S is R's mother and T is P's father; since P and R are siblings, S and T are the parents of all three, making S and T a couple (Statement I is true).

• As S and T are the parents, T is the father of Q (Statement III is true) and S is the mother of P (Statement IV is true).

• P is explicitly stated to be the brother of Q and R, so P is S's son (Statement VI is true).

• The gender of Q is not specified, so Q could be a son or daughter, making Statement II (Q is T's son) not definitely true.

• The gender of R is not specified, so R could be a son or daughter, making Statement V (R is T's daughter) not definitely true.

• Therefore, only four statements (I, III, IV, VI) are definitely true.

Why the other options are wrong

(a) Only two: Only two statements are true, but four statements (I, III, IV, VI) are definitely true.
(b) Only three: Only three statements are true, but four statements (I, III, IV, VI) are definitely true.
(d) Only five: Only five statements are true, but only four statements are definitely true because the genders of Q and R are not specified.

Asked in the CSAT Paper II of the UPSC Civil Services Preliminary Examination 2025, held on 25 May 2025. Question and answer key: Union Public Service Commission. Explanation: UPSC Answer Check.