The diagram represents blood vessels and alveoli (air sacs) in human lungs.

Question

The diagram shows branches lead into the lungs and end in air sacs. Each sac is surrounded by a dense network of blue and red veins.

Question
How does an output from the circulatory system serve as an input to the respiratory system?

Answer options with 4 options
A.
Oxygen from the veins moves into the alveoli.

B.
Carbon dioxide from the veins moves into the alveoli.

C.
Oxygen-rich blood moves from the veins into the alveoli.

D.
Carbon dioxide-rich blood moves from the veins into the alveoli.

Answer 1

The correct answer is:

B. Carbon dioxide from the veins moves into the alveoli.

In the lungs, carbon dioxide is exchanged from the blood (inside the capillaries) into the alveoli, where it can then be exhaled.