Select the correct answer. 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

D Heart rate and rate of perceived exertion

Explanation:

answer; /// i believe that the correct answer is (c); ///when the lungs expand, they fill with air from the atmosphere;

it's false.

"every person has their limitations which prevent us from accomplishing something. some are better than mathematics for example and some are worse. those people who are worse might never be able to become mathematicians, but that does not mean that they would not be great at doing something else."