The absorptive effectiveness of the small intestine is enhanced by increasing the surface area of the mucosal lining. which of the following accomplish this task?
a. plicae circulares and intestinal villi
b. the vast array of digestive enzymes
c. brunner's glands
d. the rugae

blood enters the heart through two large veins, the inferior and superior vena cava, emptying oxygen-poor blood from the body into the right atrium of the heart. as the ventricle contracts, blood leaves the heart through the pulmonic valve, into the pulmonary artery and to the lungs where it is oxygenated.