Correct option is C
From “Only A lives above B” → B must be on floor 5 and A on floor 6. “D lives immediately below B” → D is on floor 4. “Only R lives below Q” → Q must be on floor 2 and R on floor 1. The only remaining floor is 3, which must be occupied by C.
Explanation of options: (a) ✘ A is placed at the topmost floor (6), as only A lives above B. Hence, A cannot be on floor 3. (b) ✘ D is placed right below B, which means D must be on floor 4, not 3. (c) ✔ C is the only person not mentioned in any placement rules, and floor 3 is the only one left unoccupied. (d) ✘ R lives at the lowest floor, floor 1, since only R is below Q. So R cannot be on floor 3.