Which of the following will increase the reaction rate of an enzyme reaction?

decreasing the amount of enzyme while leaving the product amount unchanged
decreasing the amount of product while leaving the enzyme amount unchanged
increasing the amount of enzyme while leaving the substrate amount unchanged
increasing the amount of substrate while leaving the enzyme amount unchanged

The correct answer is "Increasing the amount of enzyme while leaving the substrate amount unchanged."

Explanation:

Activation energy is the minimum energy required to start a reaction. The role of an enzyme is to reduce the activation energy required by the substrate to start a chemical reaction. Thus an enzyme is able to speed up a reaction. By keeping the substrate amount unchanged and by increasing the enzyme amount we can ensure that there will optimal formation of the enzyme-substrate complex  which is key increasing the speed of a reaction.

Increasing the amount of enzyme while leaving the substrate amount unchanged

Explanation:

Enzymes act as catalysts (without participating in the reaction) for a given substrate in order to decrease the activation energy, thereby accelerating the reactions involving these substrates.

The enzyme concentration is directly linked to the activation energy of the reactions, and therefore, the higher the enzyme concentration, the greater the catalytic power of the enzyme and thanks to that, the rate of the enzyme reaction will be increased (assuming the enzyme is not totally saturated).