Answer: d. The rate increases because molecules are moving faster.
Step-by-step explanation:
Rate of reaction is determined by the number of effective collisions which means how many collisions are resulting into products. The molecules must possess a certain minimum energy in order to get converted to products.
Increasing the temperature means more reactant molecules will have sufficient energies to cross the energy barrier and thus the number of effective collisions increases, thus leading to more products and increased rate of reaction.