Question

in regards to cellular metabolic processes, how do oxygen levels in the air remain generally balanced?
cellular respiration uses up oxygen, while photosynthesis creates more of it.
photosynthesis uses up oxygen, while cellular respiration creates more of it.
both photosynthesis and cellular respiration use up oxygen, and the earth replaces it.
the earth uses up oxygen, and photosynthesis and cellular respiration replace it.

Explanation:

Cellular respiration is a process where cells use oxygen to break down glucose and release energy, consuming oxygen. Photosynthesis is a process in plants (and some other organisms) where they use sunlight, carbon dioxide, and water to produce glucose and oxygen. So oxygen consumption by cellular respiration is balanced by oxygen production from photosynthesis.

Answer:

Cellular respiration uses up oxygen, while photosynthesis creates more of it.