Which statement best describes why liquid water exists on earth?
a. earth experiences comet crashes and volcanic eruptions.
b. earth experiences a strong magnetic field and lunar tides.
c. earth has moderate temperatures and a strong gravitational force.
d. eath has hydrogen bonds with the sun

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.