Travis drew a model shown to describe how the body’s organs and systems meet the needs of all the body’s cells. the numbered parts of the model have not been labeled. what system does box #3 represent?

I think that this would be the excretory system.

The Digestive systems breaks down food into nutrients the body can use

The respiratory system brings in oxygen and removes carbon dioxide

The excretory system removes waste products from the body

The nervous system controls all other systems and processes information

Most likely a is the answer - because  you generate   38 atp's but also consume an atp.   each atp gives approx. less than 4 kcal so probably a is the closest answer.