A carbon cycle is a biochemical event. 

Concept: The above given statement is true.

1. The exchange of carbon between the Earth's pedosphere biosphere, geosphere, hydrosphere, and atmosphere occurs with the help of the carbon cycle, refer as biogeochemical process. 
2. Both biological substances and many minerals, that includes limestone, mostly contain of carbon. 
3. The carbon cycle is the significant process through which carbon atoms move to and fro between the Earth and the atmosphere. 
4. The carbon constituent of this near ecosystem, which includes our planet and its atmosphere, does not change. 
5. Carbon enters living organism and plants through the atmosphere.

Hence, option A is the correct answer.