Question

Oxygen is returned to the atmosphere mainly by:

• A. Burning of fossil fuel
• B. Respiration
• C. Photosynthesis
• D. Fungi

Answer 1

The correct option is C

Photosynthesis

The correct answer is option C

The explanation for the correct answer:

1. Photosynthesis is the process by which plants prepare their own food by using sunlight, water, and carbon dioxide to release oxygen and energy.
2. The amount of oxygen produced by the plant forms the basis of the oxygen that is inhaled by all animals including human beings.
3. It is the sole physiological process on the planet by which oxygen is released, without being consumed.

The explanation for the incorrect options:

Option A: Burning of fossils consumed oxygen and releases carbon dioxide.

Option B: Respiration involves the release of carbon dioxide by oxidation of the substrates in the presence of inhaled oxygen.

Option D: Fungi are heterotrophs that obtain nutrition from dead decaying matter. They do not perform photosynthesis and hence are incapable of releasing oxygen.

The final answer is option D: Photosynthesis.