Answer:
D
Explanation:
Well, animal cells use simple sugars, like glucose. The simple sugars are the only ones small enough to pass through cell walls. We use ATP to access the energy in the sugars. Cells can either use a aerobic system (using oxygen) or an anaerobic system to metabolize sugars. Humans generally use the aerobic system although in some cases our cells are forced to use the anaerobic system.
