I believe the answer is c
Answer:
facilitated diffusion
Explanation:
In facilitated diffusion, certain transport proteins of membranes (channels and carriers) serve in transport of the substances across the membrane. The movement of the amino acid occurs down the concentration gradient only. In facilitated diffusion, transport of substances occurs from the region of their higher concentration to that of the lower concentration. It is a passive process. The addition of some other amino acid slows down the transport of the first amino acid due to the saturation effect. All the transport proteins that facilitate the diffusion of amino acids across the membrane become occupied. This slows down the transport of the amino acid.
Villi provides absorption of nutrients and it's important to have that in the small intestine. As the small intestine mostly collects of nutrients of digested food. They improve absorption by providing surface area and where nutrition can be collected
Sweating
It does not involve the respiratory system.
