Concept:Pressure acts mainly on gases by changing their concentration, while solids remain nearly unaffected by pressure.
Explanation:Solids are practically incompressible, so an increase or decrease in pressure does not change their concentration meaningfully.
For gaseous reactions, pressure alters the number of particles per unit volume, which changes the rate.
However, for solids, particle size is a key factor because smaller particles provide a larger surface area for reaction.
Temperature also influences the rate of solid reactions by providing more kinetic energy to reacting particles.
A catalyst affects the rate by providing an alternative pathway with lower activation energy.
Thus, among the listed factors, pressure is the one that does not affect the rate of chemical reactions of solids.
Answer:B. pressure