Question

Which of the following best describes the events that take place when an enzyme catalyzes a chemical reaction?

Answer 1

it seems like "the following" was left out. :) Surely we can give a general answer, but it may not be what you are looking for.

Answer 2

Better give a general answer while at it:

Enzymes are proteins that catalyze chemical reactions. To fast note on catalysts are they work by decreasing the free energy of activation energy and thereby speeding up the reaction, as described by the Arrhenius equation. This decrease in free energy of activation can be the result of a altered reaction mechanism compared to the mechanism without being the substrate being enzyme bond.

The ways, the enzyme can achieve this ability are many, but the must noteworthy examples are the ability to assist proton transfer – concerted acid-base reaction, the ability of stabilizing charged intermediates, to provide a site for a great lose in entropy ("freezes" translation and rotation) and provide a hydrophobic environment for the reaction to occur if required.