Which two statements explain why oxygen is vital to sustaining a healthy
ecosystem?
A. Atoms of oxygen are part of the biomolecules that make up all
living things.
B. Oxygen gas is needed for the combustion reactions that release
energy from fossil fuels.
C. Oxygen is a reactant in cellular respiration, which supplies energy
for life processes.
D. All of Earth's heterotrophs depend on oxygen as a source of
energy for life processes.
