Study the reactions.
I. N2(g)+O2(g)→2NO(g)
II. CO(g)+12O2(g)→2CO2(g)
III. Na(s)+HCl(l)→2NaCl(aq)+12H2(g)

What factor would only affect the rate of the third reaction?

Responses
a. the surface area of the reactants
b. the pressure of the reactants