I think the answer is C because many teens and adults have unsafe lifestyles that lead to injury and death.
To prevent injuries, because if you are running around and exercising, if you haven't warmed up, you could pull a muscle or injure yourself. Cool downs help calm your body down and lower your heart rate.
Some of the reasons can be:
If you're a pre-teen or a teenager who has only started menstruating, you may find that it takes a while for your period to settle in and become regular.
I couldn't think of anything else, but hope this helped enough!
To find the best answer, ask your mom!
~Aurora
