For a certain reaction a large fraction of molecules has energy more than the threshold energy, still the rate of reaction is very slow. The possible reason for this could be that

Options

A. the colliding molecules could be large in size
B. the colliding molecules must not be properly oriented for effective collisions
C. the rate of reaction could be independent of the energy
D. one of the reactant cound be in excess.

Answer

B

Explanation

Apart from energy considerations the colliding molecules should have proper orientation for effective collisions.