Answer: The answer to your question is A.
Explanation: The other user who answered this was incorrect however it could have just been a mistake. But a catalyst speeds up the reaction rate. :) The reason the answer is A is because Increasing the surface area of a solid reactant exposes more of its particles to attack. This results in an increased chance of collisions between reactant particles, so there are more collisions in any given time and the rate of reaction increases.
I hope this helps you out lots! :D