Which of the following are the sites within the human body where carbon dioxide and oxygen are exchanged?

A. Alveoli
B. Arteries
C. Synapses
D. Venules

I think A

Agree.

You are correct, the sites within the human body where carbon dioxide and oxygen are exchanged are the alveoli. To arrive at this answer, you can use your knowledge of the respiratory system.

The alveoli are tiny air sacs found within the lungs. They are the primary sites of gas exchange in the respiratory system. When we inhale, oxygen is taken in and diffuses across the walls of the alveoli into the bloodstream. At the same time, carbon dioxide, a waste product of cellular respiration, diffuses from the bloodstream across the alveoli walls and is exhaled during expiration.

Therefore, option A, alveoli, is the correct answer. The other options, arteries (option B), synapses (option C), and venules (option D), do not play a direct role in the exchange of carbon dioxide and oxygen.