Why do many gas-phase reactions occur with rapid kinetics, whereas solid-phase reactions occur slowly?

a. In gas phase reactions, the reactants are more abundant and so the reaction is faster.

b. In solid phase reactions, the reactant are more stable and therefore reactions do not occur readily.

c. Gas phase reactions occur faster because the particles will collide much more frequently - and with greater energy - than with solid phase reactions.

d. no right choice