How is carbon reintroduced into the atmosphere?
a. respiration
b. photosynthesis
c. evaporation
d. all of the above

The correct answer would be a. respiration.

In the atmosphere, carbon is present in the form of carbon dioxide. It forms the major components of organic substances or molecules. It is majorly fixed in the ecosystem by process of photosynthesis.

The number of processes or activities help to reintroduce carbon into the atmosphere. Some of them are:

Respiration: Most of the living organisms release carbon dioxide in the atmosphere through respiration. They harnessed energy from food and release carbon dioxide as the byproduct of the process.

The burning of fossil fuels also releases a huge amount of carbon dioxide in the atmosphere.

Volcanic irruptions, forests fires et cetera also release carbon dioxide in the atmosphere.

Hence, we can say that respiration helps in reintroducing carbon into the atmosphere.

it provides an alternative energy pathway for the reaction to proceed.

a catalyst is a substance that speeds up the rate of a chemical reaction but is not consumed during the course of the reaction.

catalysts increase the rate of reaction without being used up. they do this by lowering the activation energy needed. with a catalyst, more collisions result in a reaction, so the rate of reaction increases. different reactions need different catalysts.

a catalyst works by providing an alternative reaction pathway to the reaction product. the rate of the reaction is increased as this alternative route has a lower activation energy than the reaction route not mediated by the catalyst.