Which of the following statements about the left ventricle is/are true? a. blood entering the left ventricle is usually quite low in its oxygen concentration. b. blood exits the left ventricle through the aortic valve into the aorta. c. the left ventricle contracts at the same time as the left atrium. d. the wall of the left ventricle is very thin but also is very strong. e. both b and d are correct.

B. Blood exits the left ventricle through the aortic valve into the aorta

Explanation:

- Blood entering the left ventricle is usually quite high in its oxygen concentration. Atria are the thin walled receiving chambers. The right atrium receives the deoxygenated blood from different parts of the body through superior and inferior vena cava. Left atrium receives the oxygenated blood through pulmonary veins. This oxygenated blood then passes to the left ventricle when bicuspid valve opens.

- Atrial systole i.e atrial contraction occurs for a period of 0.1 second which is followed by the ventricular contraction for a period of 0.3 seconds. For a time period of 0.4 seconds both ventricles and auricles are in diastolic phase which is refereed as joint diastole.

- Ventricles are thick walled blood pumping chambers and in fact the left ventricle is thicker than that of the right ventricle. The thicker walls of left ventricle are useful for pumping the blood to all the body parts though aorta guarded by aortic valve.

substitution is the answer in this case

i think the answer is b.