Question

Oxygen is returned to the atmosphere mainly by
A) Burning fossil fuels
B) Respiration
C) Metabolism
D) Photosynthesis

Answer 1

The term oxygen usually applies to the most abundant oxygen allotrope, diatomic oxygen, as many biogeochemical redox reactions inside the cycle are a simple option or reactant.

Complete answer:
First we should know about barley oxygen cycle to answer this question. One of the most common elements on Earth is oxygen, which accounts for a significant portion of each major reservoir. The oxygen cycle, by redox reactions inside and between the reservoirs of the planet Earth, is the earth's natural transition of oxygen atoms between various oxidation states of oxides, ions, and molecules.
Now, let us find the solution from the options-
- Around 35 billion tons of carbon dioxide dioxide are emitted each year by the combustion of fossil fuels. CO2 is a greenhouse gas that raises the radiative force and leads to global warming and acidification of the ocean. To aid decrease global greenhouse gas emissions, a global trend for the production of low-carbon renewable energy is ongoing. Thus, option A is not the correct option.
- Respiration is the release of oxygen to the cells inside the tissues from the external environment, and the delivery of carbon dioxide in the same direction. Thus, option B is not the correct option.
- Metabolism is the array of chemical reactions in organisms that support life. The three key metabolism goals are: the processing of food into energy to power cellular processes; the transformation of food / fuel to protein, nucleic acid, lipid, and some carbohydrate components; and the reduction of metabolic waste. These enzyme-catalyzed reactions facilitate the growth and reproduction of species, the preservation of their structures and the response to their environments. Thus, option C is not the correct option.
- Animals absorb oxygen from the environment to carry out the respiration process. Photosynthesis is the mechanism in which, in the existence of sunlight, autotrophs like green plants utilize carbon dioxide and water to produce nutrients like carbohydrates in glucose form and produce oxygen. Oxygen is then returned through photosynthesis to the atmosphere.

Thus, the correct option is option (D) Photosynthesis.

Note: The greatest source of Earth's oxygen is by far (99.5 percent by weight) within the silicate or oxide minerals of the crust and upper mantle. The Planet's atmosphere, hydrosphere, and biosphere combined comprise below 0.05% of the total oxygen mass of the Earth.