High concentrations of carbon dioxide are harmful to the human body. The heart and the lungs work together to keep the body’s carbon dioxide level low. When the amount of carbon dioxide in the blood gets too high, the heart beats faster and the lungs begin to exhale more rapidly. This allows the lungs to remove the carbon dioxide from the blood and expel it from the body faster. Based on the information, select the two body systems that work together to maintain a low carbon dioxide concentration in the body.

There are two correct answers. Select both answers.

a
digestive system
b
circulatory system
c
respiratory system
d
nervous system