If your heart is not strong enough or efficient enough, it is difficult to
a. strech
b. lift weights
c. breath
d. perspire

  C.) Breathe

Explanation:   Your heart pumps oxygen, and pushes out carbon dioxide, so if your heart is not strong enough or efficient enough then it is more difficult to breathe.

answer; i believe the correct answer is (d) are very restrictive in the choice of care.

answer; i believe that the correct answer is (essential amino acids);