Ling decided to do a science project on exercise. She wanted to find out how long it takes for a person's heart rate to slow down to normal after exercise. Which of the following was likely the scientific prediction Ling made about her project?
A.
My heart beats 60 times each minute.
B.
Exercise is important.
C.
A person's heart rate slows down in three minutes.
D.
I found out that my heart beat slows down after five minutes.