Answer:
The correct answer is (A)recycled through the activity of living and nonliving systems.
Carbon dioxide and oxygen are important resources of any ecosystem. Oxygen is essential for all living beings as it is required in cellular respiration (aerobic) while carbon dioxide is used as a source of carbon in plants for producing sugar and other essential nutrients.
In an ecosystem, resources including oxygen and carbn dioxide are recycled through the activity of both living and non-living systems.
For example, carbon dioxide is used by plants (living) and is released by living system such respiration of animals and plants and decaying of dead animals and plants . In addition, it is also released by non-living system such as burning of fossil fuels, biomass combustion, volcanic eruptions etc. In this way carbon dioxide keeps cycling in an ecosystem.
Similarly, oxygen is also cycled with the help of living and non-living systems. For example, it is released in atmosphere as a byproduct of photosynthesis and is used by all living organisms. Non-living system such as photolysis of water also helps in release of some amount of oxygen in an atmosphere.
