How is the growth of land plants proof that there is carbon in the atmosphere ? how does carbon exist in the atmosphere biosphere and geosphere all at the same time?

Carbon is one of the most important elements on earth all living things are made up of carbon. Gas is made from carbon such as carbon dioxide playing an important role in regulating the climate. Biological activities cause the carbon to be constantly converted among different forms. There is an exchange of carbon from the atmosphere, vegetation, soils and organic matter, ocean and fossil fuels, these changes are continually changing. The carbon cycle is the cycle by which carbon is exchanged among the biosphere, geosphere, and atmosphere of the Earth.  

Let’s look an example of a volcano and how it contributes to the atmosphere biosphere and geosphere all at the same time. The volcanic eruption occurs in the geosphere and the gases are released into the atmosphere whilst the lava will flowing down will disrupt the biosphere.

b. lithosphere, asthenosphere, mesosphere   is the answer most likely