Final answer:
The two semilunar valves of the heart are the aortic valve and the pulmonary valve, which prevent backflow of blood from the aorta and pulmonary artery into the ventricles. The correct answer is b. Aortic and pulmonary valves.
Step-by-step explanation:
The Semilunar Valves of the Heart
The names of the two semilunar valves in the heart are the aortic valve and the pulmonary valve. These valves are named for the arteries they feed into - the aorta and the pulmonary artery, respectively. Unlike the atrioventricular valves, which include the tricuspid and the mitral (or bicuspid) valves, the semilunar valves are shaped like half-moons and play a crucial role in preventing backflow of blood from the arteries back into the ventricles.
The correct answer to the question is b. Aortic and pulmonary valves. The aortic semilunar valve sits at the exit of the left ventricle and opens to allow oxygen-rich blood to flow into the aorta and throughout the body. The pulmonary semilunar valve sits at the exit of the right ventricle and opens to allow oxygen-depleted blood to flow into the pulmonary artery and on to the lungs for oxygenation.