What two things can you use to determine how hard your body is working? A.) Heart rate and muscle stiffness

B.) Rate of perceived exertion and breathing rate

C.) Muscle stiffness and breathing rate

D.) Heart rate and rate of perceived exertion

It literally could be all of them

Explanation:

Perceived exertion is how hard you feel like your body is working. It is based on the physical sensations a person experiences during physical activity, including increased heart rate, increased respiration or breathing rate, increased sweating, and muscle fatigue.

the correct answer would be a.=) have a great day!

answer; /// an alphabetical list of sources arranged according to a citation style and followed by a summary of the content;