Answer:
The amount of carbon in the trees and in the deer . . .
A) has increased.
Step-by-step explanation:
Carbon is the basis for all living cells, it is responsible for the making and storing of energy. So if the number of energy storage molecules increases, the amount of carbon will increase because carbon is used to make those molecules.
Your question on carbon dioxide and photosynthesis having an effect is valid, but the loss of carbon wouldn't be much compared to the energy storage molecules, so we wouldn't consider that a factor in this case.