How would adding the catalyst nitrogen monoxide (NO) affect this reaction? 2SO2(g) + O2(g) → 2SO3(g)

A.
NO increases the rate at which SO3 molecules are formed.
B.
NO reacts with SO3 to produce more SO2 molecules.
C.
NO decreases collisions between the SO2 and O2 molecules.
D.
NO increases the concentration of the SO2 and O2 molecules.
E.
NO increases the activation energy of the SO2 and O2 molecules