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