Which statement is an example of a scientific theory?
A. All living organisms are composed of one or more cells, which came from pre-existing cells.
B. Hummingbirds do not like the color white because they visit other colored flowers more often.
C. The amount that caffeine affects a person's heart rate differs based on the person's age.
D. The Earth is the third planet from the Sun and has one moon, which orbits the Earth.