Question

animals breathe in and absorb ____ gas needed for cellular respiration and breathe out ____ gas as a waste product of cellular respiration.

breathe in
?
breathe out
?

oxygen, carbon dioxide
carbon dioxide, oxygen
nitrogen, oxygen
methane, nitrogen

Explanation:

Cellular respiration in animals requires oxygen and produces carbon - dioxide as a waste product. Animals inhale oxygen and exhale carbon - dioxide.

Answer:

A. oxygen, carbon dioxide