Because their bodies tell them that they need more oxygen and so breathe faster, and try and get the oxygen their body requires and depends on.
Answer:
♡hi there! ♡
good combo of words and numbers! ʕ •ᴥ•ʔ
hope I could help! have a great day
-madeline
✧・゚: *✧・゚:・゚✧*:・゚✧・゚: *✧・゚:・゚✧*:・゚✧
Explanation:
Hey if I help you have to help me