Final answer:
Most nutrients are absorbed through the mucosa of the intestinal villi via B) active transport, which requires energy in the form of ATP. This process is distinct from other passive mechanisms such as simple or facilitated diffusion.
Step-by-step explanation:
The absorption of most nutrients through the mucosa of the intestinal villi is a process that requires active transport, which is fueled by ATP (adenosine triphosphate). This transport mechanism involves moving substances from an area of lower concentration to an area of higher concentration and requires specific proteins that act as pumps. This is different from passive mechanisms like simple diffusion, in which substances move along the concentration gradient without the use of cellular energy. There are various mechanisms by which nutrients can be absorbed in the small intestine, such as passive diffusion, facilitated diffusion, co-transport, endocytosis, and the aforementioned active transport. Water-soluble nutrients, which cannot easily pass through the hydrophobic plasma membrane, typically rely on transport molecules or such energy-dependent mechanisms to enter cells. However, lipid-soluble nutrients can diffuse through the plasma membrane without requiring ATP.