What is the function of fold and villi

Option A.

Explanation:

Villi are the finger like projection present in the surface of small intestine in circular folds.

Villi is the organelle that functions to increase the surface area ( internal surface) of small intestine walls and provide more surface area for absorption. The increased surface area increases absorption of useful nutrients such as amino acid and monosaccherides and that passes into the semipermeable villi with the process of diffusion. Villi decreases the average distance travelled by nutrient molecules due to increased surface area and hence diffusion increases.

Hence, the correct option is A.

answer; polycythemia is the correct answer;

the tricuspid valve is present between right atrium and right ventricle