Which statement is true?
a. lipids are a type of fat.
b. fats are a type of lipid.
c. fats and lipids are separate and unrelated substances.
d. all lipids are fats, and all fats are lipids.

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.