Enzymes called kinases are responsible for
a. removing electrons from substrates
b. enzymes that catalyze the transfer of protons from one molecule to another
c. adding hydrogens to substrates
d. adding phosphate groups (i. e., phosphorylation of substrates)

The correct answer is d. adding phosphate groups (i.e., phosphorylation of substrates)

Explanation:

Kinases are enzymes which transfer a phosphate group from ATP (adenosine triphosphate) to a sustrate. With the adding of the phosphate group, the sustrate can be activated or disactivated. Usually, kinases are involved in "phosphorylation cascades" which regulates biological processes.