Final answer:
The small intestine in biology is involved in the digestion and absorption of nutrients. The villi increase the absorption surface area. A form measuring 45 um in stool could be a microscopic organism or cell.
Step-by-step explanation:
The student is asking about a form measuring 45 um found in stool. In biology, the small intestine plays a crucial role in the digestion and absorption of nutrients. The villi, fingerlike projections on the intestine walls, greatly increase the surface area for absorption. Stool is composed of undigested food residues, unabsorbed digested substances, bacteria, old epithelial cells, inorganic salts, and water. If something measuring 45 um is found in stool, it could be a microscopic organism or a cell.