Final answer:
A parietal cell, involved in producing stomach acid and intrinsic factor, is much bigger than a glucose molecule, which is a small simple sugar.
Step-by-step explanation:
A parietal cell is significantly bigger than a glucose molecule. Parietal cells are specialized epithelial cells located in the stomach and are involved in producing hydrochloric acid (HCl) and intrinsic factor, playing a key role in digestion. In comparison, glucose is a simple sugar, a small organic molecule, which is a component of the food we digest. Therefore, the correct answer to the question is 'a) Bigger'.