Answer: carbon dioxide
Step-by-step explanation:
This question is referring to the function of the respiratory system in the body and the lungs with the respiratory system are allowing us to breathe.
The lungs are bringing at first oxygen into our body and that process is called inspiration or also inhalation. They are sending carbon dioxide out which is a process that is called exhalation or also expiration.
This is the exchange that is happening in our body and with that exchange of oxygen and carbon dioxide, it is called respiration.