The main function of the small intestine is nutrient absorption. which of the following structural qualities of the intestine increase absorption? select all that apply.
a. very long tube almost 6 meters in length when relaxed
b. internal wall covered with fingerlike projections called villi
c. cell membrane of epithelial cells with multiple foldings
d. higher ph than in the stomach, in part by secretion of bicarbonate

The correct answer will be option a and b.

Explanation:

The food is digested and absorbed in the small intestine, a long folded tube which lengths about 20 ft or 6m.  

The small intestine increases the surface area for food absorption as they have circular folding as well as the finger-like projections called villi and microvilli in the lumen of the intestine. These villi help in absorption of the nutrients from the intestine.

Thus, option a and b are the correct options.

many other transport proteins, often called pumps, move materials against a concentration gradient. active transport drives molecules across a membrane from a region of lower concentration to a region of higher concentration. this process, shown in figure 5.1, uses transport proteins powered by chemi- cal energy.