How/why does this brown, clumpy mixture come out of your bottom?

Plants transfer carbon in the carbon cycle a. through assimilation of carbon from the soil. b. when carbon transpires from their stomatae. c. when they are eaten by animals. d. through fixation of carbon in the soil.plants transfer carbon in the carbon cycle a. through assimilation of carbon from the soil. b. when carbon transpires from their stomatae. c. when they are eaten by animals. d. through fixation of carbon in the soil.