Answer:
because theyre in our bodies and they have to be small to be in our bodies
Explanation:
Answer:
A.
Explanation:
All other options are simply situational, while cold periods are usually seasonal.
While photosynthesis requires carbon dioxide and releases oxygen, cellular respirationrequires oxygen and releases carbon dioxide. It is the released oxygen that is used by us and most other organisms for cellular respiration. We breathe in that oxygen, which is carried through our blood to all our cells.