Correct option is C
Given:
T lives on floor number 4.
T lives immediately above P. (P lives on floor number 3)
U lives immediately above Q.
R lives immediately below S.
Exactly three persons live between R and Q.
Q does not live on floor number 5.
From the given information arrangement will be:

Here, S lives on the 6th floor.
Thus, correct option is (c)