It takes about [?] hours for food to be ingested, digested, and leave the small
intestine.
A. 8
B. 1-2
C. 24
D. 5.

A 6 to 8 hours. After you eat it takes about 6 to 8 hours for food to pass through your stomach and small intestine.

the oxygenated blood then leaves the lungs through pulmonary veins, which return it to the left heart, completing the pulmonary cycle. this blood then enters the left atrium, which pumps it through the mitral valve into the left ventricle. from the left ventricle, the blood passes through the aortic valve to the aorta.

deoxygenated blood leaves through the right ventricle through the pulmonary artery. from the right atrium, the blood is pumped through the tricuspid valve (or right atrioventricular valve), into the right ventricle.

answer: substrate concentration. enzymes work best when there is a high enough substrate concentration for the reaction they catalyse.