P , Q, R, S, T and U are six members of a family. R is the spouse of Q. U is the mother of T and S is the daughter of U. P’s daughter is T and R’s son is P . There are two couples in the family. Which one of the following is correct?

The correct option is "T is the granddaughter of Q".

Let us analyze the relationships step-by-step to understand the structure of the family tree:
1. R is the spouse of Q: This means R and Q are married to each other. They form one of the two couples in the family. We do not know their genders yet.
2. R's son is P: Since R and Q are married, P is the son of both R and Q. P is male.
3. P's daughter is T: This tells us that T is female and is the daughter of P. Since P is the son of R and Q, T must be the granddaughter of R and Q.
4. U is the mother of T: Since T's father is P, and U is the mother of T, P and U must be married to each other. This forms the second couple in the family. P is male, and U is female.
5. S is the daughter of U: Since P and U are married, S (who is the daughter of U) is also the daughter of P. Therefore, S and T are sisters (both daughters of P and U).

Now, let us trace the generations:
- First Generation (Grandparents): Q and R (Couple 1)
- Second Generation (Parents): P and U (Couple 2, where P is the son of Q and R)
- Third Generation (Children): T and S (Daughters of P and U)

Since T is in the third generation and is female, T is indeed the granddaughter of both R and Q.
Therefore, the statement "T is the granddaughter of Q" is correct.