The correct answer is option c. Carbon.
The carbon cycle is the biogeochemical cycle, in which the plants take up carbon from air as carbon dioxide and convert it into glucose and other carbon containing compound, which is used by animals in cellular respiration and produce carbon dioxide. The produced carbon dioxide is transferred back to the air. The organic material of the plants and the animals are buried in soil and cause the formation of the fossil fuels, which is used as a source of fuel. the burning of the fossil fuels also produce carbon dioxide.
Hence, the burning of the fossil fuel in the factory causes the transfer of carbon dioxide in the air, which is taken by plants and then the carbon product made by using the carbon dioxide is transferred to the animals. hence, the movement of the carbon is shown by the flowchart.