A, B, C, D, E and F live on six different floors of the same building. The lowermost floor in the building is numbered 1, the floor above it, number 2 and so on till the topmost floor is numbered 6.
A lives on a floor which is a prime number. The product of floors on which A and E live is 3. Only 2 people live above B. F lives immediately below C. How many people live between D and F?

Given: A, B, C, D, E and F live on six different floors of the same building. The lowermost floor in the building is numbered 1, the floor above it, number 2 and so on till the topmost floor is numbered 6.

1) A lives on a floor which is a prime number.

2) The product of floors on which A and E live is 3.

The only two floor numbers whose product is 3 are 1 and 3. Since A lives on a prime number floor, A must live on floor 3, and E must live on floor 1.

3) Only 2 people live above B.

4) F lives immediately below C.

The only consecutive empty floors are 5 and 6. So C lives on Floor 6 and F lives on Floor 5.

The remaining person is D, who must live on the remaining empty floor, which is Floor 2.

Thus, two people live between D and F.

Hence, the correct answer is "Option 1".