Question

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

Explanation:

Cellular respiration is a process where cells break down glucose and use oxygen to release energy, thus 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, cellular respiration uses oxygen and photosynthesis creates oxygen, which helps in maintaining the balance of oxygen levels in the air.

Answer:

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