Answer:
D: It will increase because smaller particles provide more surface area to react.
Step-by-step explanation:
When the large iron is broken up into smaller pieces, there are more places for the iron to react (meaning there's more surface area). Think of it like taking the surface area of a big cube compared to the surface area of a bunch of small cubes. The sum of the surface areas of the small cubes will be greater than that of the large cube. As a result, more places for the iron to react will cause for a greater reaction.