Enzymes influence chemical reactions in living systems by

Often, reactants are found in low concentrations. Because the reactions must take place very quickly, they usually need a catalyst. Enzymes are catalysts for chemical reactions in living things. Enzymes, like other catalysts, lower the activation energy and increase the rate of chemical reac- tions.

hope this helps!

(im only a 6th grader so I might be wrong but this is how i define it)

correct answer is a. and d.