Why does a steeper approach cause an increased landing rollout?
I'll just formalize my comment here as an answer:

Landing is all about managing the aircraft's energy. When you are coming in for a landing with a steep approach it usually means that you will have more energy (speed) as you approach the ground. A high ground speed as you approach the runway usually means floating and/or, just like in a car, a longer distance to slow down. That extended distance you would need to bring the plane to a stop or slow enough to taxi off the runway would be the extended roll-out. Therefore B is the best answer.

A is incorrect because a steep approach does not necessarily mean a hard landing. The smoothness of a landing is dependent on the pilot knowing the appropriate moment to flare.

C is incorrect because unless the pilot is trying to land short of the threshold a steep approach can be done anywhere over any part of the runway/approach.