The answer is C. Both A & B.
Enzymes are proteins that act as biological catalysts. They speed up the rate of chemical reactions without being consumed by the reaction. Enzymes work by lowering the activation energy, which is the energy required to start a chemical reaction. This is done by providing a specific environment for the reactants to interact in, which makes it easier for them to form the products of the reaction.
For example, the enzyme catalase breaks down hydrogen peroxide into water and oxygen. The activation energy for this reaction is very high, but catalase lowers the activation energy by providing a specific environment for the reactants to interact in. This makes it much easier for the reactants to form the products of the reaction, and the reaction proceeds much faster.
Enzymes are essential for life, as they are responsible for catalyzing the vast majority of chemical reactions that take place in cells. Without enzymes, these reactions would take place much too slowly for life to exist.