Why are enzymes necessary? to the rate of decomposition to act as a catalyst in chemical reactions to conserve the stored energy of a cell

Option B, to act as a catalyst in chemical reactions

Explanation:

Enzymes are organic bio molecules that act as catalyst to increases the rate of a bio-chemical reaction involved in any biological process. All enzymes are made of amino acids and have suffix -ase at the end of their name.

For example -

Enzyme Amylase catalyses the chemical processes involved in the digestion of sugar in mouth. It increases the rate of conversion of  starch molecules into smaller glucose and maltose molecules.

Thus, option B is correct

a. decomposes use carbon from dead organisms as fuel for cellular respiration, returning carbon dioxide back into the atmosphere.