The correct answer is (c). Similar poles repel.
When two steel pins are stuck to the end of a bar magnet, the poles of the pins that are facing the magnet are the same as the pole of the magnet. This means that the two pins are repelling each other, which causes them to tilt away from each other.
(a) is incorrect because the heads of the pins do not need to be perfectly rounded in order to stick to the magnet. As long as the heads of the pins are close enough to the magnet, they will be attracted to it.
(b) is incorrect because the spherical shape of the heads of the pins does not affect the way that they stick to the magnet. The only thing that matters is the distance between the heads of the pins and the magnet.
(d) is incorrect because the two pins do not hang vertically because of the fact that similar poles repel.