Answer:
Due to difference in volume of both atmosphere.
Explanation:
There is difference in volume of carbondioxide and oxygen gas between the atmosphere and the exhaled air because of the volume difference of atmosphere and exhaled air. The volume of atmosphere is larger than the body from where the gases are exhaled. The body has lower space for these gases so these gases are less in concentration in the exhaled air which the body releases as compared to the atmosphere where the concentration of these gases are larger.