Answer:
Option A, increasing the surface area of the salt
Explanation:
For a reaction to occur, there must be collision between reactant molecules. One of the factor that increases the collision between reactant molecules is surface area of the solid reactant. Therefore, increase in surface area, increases the rate of reaction.
For example, consider reaction between calcium carbonate and hydrochloric acid
Calcium carbonate is solid and powered calcium carbonate reacts faster because of increase in surface area.
Therefore, among the given option, A is the correct answer.