Carbon dioxide is present in nature is taken by the green plants to make their food. The process of making food by green plants by utilizing carbon dioxide and water in the presence of sunlight is called photosynthesis. Therefore photosynthesis is the process that takes in the CO₂ in the carbon cycle.
Respiration is the process by which the oxygen is taken in the body by living organisms and CO₂ is released out in the environment. So respiration is the process which returns carbon to the atmosphere in the carbon cycle.
Some of the CO₂ is also released by automobile industries and other industries as a waste product through emission which is also a part of the carbon cycle.
African trypanosomiasis is a parasitic disease transmitted by the tsetse fly. It gets its nickname 'sleeping sickness' because symptoms can include a disturbed sleep pattern.
I think it the answer is C ( The relationship between the bacteria and the ticks is commensalism, and the relationship between ticks and humans is parasitism. -- Alina (:
