The right answer is the activation energy.
The catalyst increases the reaction rate by introducing new reaction paths (mechanism), and lowering its activation energy, or activation Gibbs free energy. By doing this it can increase the speed, or lower the temperature of the reaction. It is important to note that the catalyst does not alter the total Gibbs free energy of the reaction which is a system state function and therefore has no effect on the equilibrium constant.
C.there is no relationship between metabolic rate and body temperature.
