Brain death occurs when: a. a person remains unconscious for a specified period of time. b. the lower regions of the brain stop functioning. c. all electrical activity of the brain has ceased for a specified period of time. d. the body loses the ability to breathe on its own.

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.