During cellular respiration, every living thing in this food web uses gas and releases back into the environment.
a. carbon dioxide: oxygen
b. oxygen: carbon dioxide
c. carbon dioxide: hydrogen
d. carbon dioxide: water vapor

what statement best describes the difference between the sympathetic and parasympathetic nervous systems?

the sympathetic nervous system prepares the body for intense physical activity and is often referred to as the fight-or-flight response. the parasympathetic nervous system has almost the exact opposite effect and relaxes the body and inhibits or slows many high energy functions.