Concept:The villi are tiny finger-like projections in the small intestine that help absorb digested food.
Explanation:The villi greatly increase the internal surface area of the small intestine.
A larger surface area allows digested nutrients to be absorbed into the blood and lymph quickly.
They do not secrete gastric juice, curdle milk, or emulsify fat.
These functions belong to other parts of the alimentary canal.
Therefore, the main role of the villi is to enhance absorption.
Answer:D. increase the surface area for absorption