The rate of reaction can be increased by

A) Decrease in threshold energy represents decrease in high of the energy barrier which cause to need less activation energy Hence rate of reaction also increases. The minimum amount of energy which the colliding molecules must possess as to make the chemical reaction to occur is known as threshold energy (E). 

B) A catalyst may increase (positive catalyst) or decrease (negative catalyst) the rate of a reaction without undergoing any chemical change

 C) If the activation energy is low, the fraction of effective collisions will be large and the reaction will be fast. But the given statement is by increasing activation energy rate of the reaction can be increased. 

D) When temperature is increased, the number of active molecules increases i.e. The number of effective Collisions will increase and the rate of reaction will increase.