Most nutrient absoprtion occurs here
a. large intestine
b. jejunum
c. duodenum
d. stomach
e. ileum

b. Jejunum

Explanation:

The small intestine is divided into three regions: duodenum, jejunum, and ileum. The jejunum is the middle region of the small intestine and is rich in folds and villi to facilitate the absorption of most of the digested carbohydrates and proteins. The small finger-like projection, the villi, increase the surface area for the absorption of digested nutrients.  

Circular folds are the folds of mucosa and submucosa of intestinal lining while villi are the projections of the mucosa into the cavity of the small intestine. Circular folds, villi, and microvilli facilitate the absorption of most of the nutrients in the jejunum.  

the tricuspid valve is present between right atrium and right ventricle