Which Statement About the Slow Step in the Mechanism for a Reaction

Which statement about the slow step in the mechanism for a reaction mechanism is true?

A) It has a rate that is independent of the activation energy for the reaction.
B) It limits the effectiveness of a catalyst.
C) It controls the rate at which the products are produced.
D) It almost always involves the breaking of hydrogen bonds.
E) It determines the value of the standard enthalpy of reaction for the reaction.