This cardiovascular event may occur when there is a sudden loss of blood flow to the cardiac muscle causing cardiac muscle cells to stop functioning.
a. stroke
b. heart attack
c. hypertension
d. atherosclerosis

they need it to survive

explanation:

the more fit you are, the faster the recovery. your heart rate drops most sharply in the first minute after you stop exercising; it should then fall about 20 beats a minute—a drop of less than 12 beats a minute is considered abnormal. this “recovery heart rate” is measured as part of an exercise stress test.