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.

Which of the following best describes the expensive tissue hypothesis? brains require more energy, so the gut had to be reduced, and larger brains and tool use led to higher quality diets. increasing body size means that homo neanderthalensis had to include more fat in its diet. brains require more energy, so the gut had to be reduced as brains got bigger. brains require more fat, so the gastrointestinal viscera (gut) had to expand, and hands were needed to acquire more food.