Circular folds and intestinal villi Circular folds and intestinal villi
a. produce hormones.
b. increase the surface area of the mucosa of the small intestine.
c. produce new cells for the mucosa of the small intestine.
d. carry products of digestion that will not pass through the walls of blood capillaries.
e. secrete digestive enzymes.

Option B. "increase the surface area of the mucosa of the small intestine."

Explanation:

Circular folds and intestinal villi present in small intestine and performs function of increasing the surface area of mucosa and support absorption.

The circular folds are projected towrads lumen in small intestine showing valvular flaps. The circular folds are further covered by finger like projection called intestinal villi.

The circular folds functions by slowing down the passage of food which is partly digested and with the help of villi it increases the mucosal surface area and further support  absorption of fatty acids in blood.

Hence, the correct option is B.

a. the production of carbon dioxide through the process of photosynthesis