They have more little impact because they are renewable
Homologous structures are common structures in different species that perform different functions and may have look similar in structure.
Example- The different animals have bones that appear very similar in form and function and seem to be related.
Metabolism, respiration and digestion are all complex chemical processes involving many steps, happening in 3 dimensional space within cells. Metabolism is the breaking of bonds within food molecules (like sugar) to harness energy for cellular work; respiration involves moving oxygen and carbon dioxide gases between cells to facilitate cellular metabolism and digestion involves breaking down food macro structures into smaller units suitable for metabolism.
So the answer is D - each of the three process involve multiple chemical reactions.
