From the observations, we know that A & B are attracted to each other, but B does not attract C.

For (1), A & B are unlike poles, so they can attract each other. C is non-magnetic material, so B cannot attract C.

(2) is incorrect because the second part contradicts. A & B are unlike poles and can attract. But C is steel which is magnetic material, so B can also attract C.

(3) is incorrect because B is not magnetic material, so no magnet can attract B. As for A, the name "steel block" suggest that it may be just normal unmagnetised steel block.

(4) is incorrect because A is not magnetic material, so B will not be able to attract A.

Final answer : (1)

Note that for this experiment, we can tell that A and B CAN be unlike poles of magnets, but not necessary MUST be. If one of them is a magnet, and the other one is just normal magnetic material, we will still get the same observations.

Only when 2 objects repel, then we can be sure that both MUST be magnets because only like poles of magnets can repel each other.

Thank you Boy Mow Chau! That was a really helpful explanation! Really appreciate it a lot! :D