From the left ventricle, blood flows most directly into which structure?

A. aorta
B. vena cava
C. right ventricle
D. left atrium

http://science.howstuffworks.com/life/human-biology/heart3.htm

To determine the structure into which blood flows most directly from the left ventricle, we need to understand the basic anatomy of the heart.

The left ventricle is one of the four chambers of the heart, located at the bottom left-hand side. It is responsible for pumping oxygenated blood received from the left atrium out of the heart and into the systemic circulation.

Now, looking at the answer options:

A. The aorta is the largest artery in the body that carries oxygenated blood from the heart to the rest of the body. The left ventricle indeed pumps blood directly into the aorta, so this could be the correct answer.

B. The vena cava is a large vein that returns deoxygenated blood from the body back to the heart. Blood does not flow from the left ventricle directly into the vena cava, so we can eliminate this option.

C. The right ventricle is another chamber of the heart, but it receives deoxygenated blood from the right atrium and pumps it to the lungs. Blood does not flow directly from the left ventricle into the right ventricle, so we can eliminate this option as well.

D. The left atrium receives oxygenated blood from the lungs and then passes it to the left ventricle. So, blood initially flows from the left atrium into the left ventricle, but it does not flow most directly into the left atrium from the left ventricle.

Considering the information provided, the correct answer is A. aorta, as blood flows most directly from the left ventricle into the aorta.