Answer the following question given this paragraph: 

There must be more to this story than just gas exchange with the environment. To begin to appreciate the role of oxygen inside your body, think about when your breathing rate increases: climbing a steep slope, running a race, or skating a shift in a hockey game. Respiration rate correlates with energy use, and that correlation reflects the link between oxygen and energy metabolism. For this reason, the chemical process inside your cells that consume oxygen to produce usable energy is known as cellular respiration . During this process, energy is converted from glucose , in the presence of oxygen, into numerous ATP molecules. The glucose, of course, comes from the food you eat. In biological terms, you do not eat because you are hungry, you eat to get energy. Other heterotrophic organisms also acquire glucose from other organisms, whereas autotrophic organisms make their own glucose, mostly through photosynthesis.


Q: Respiration rate correlates with what?

 Choices:

- size

- heat

- pressure

- energy use

A:
energy use
