47 What is the main idea of this passage?
(A)The ratio of the brain size relative to the body size of an animal is a good measure of intelligence.
(B)The number of neurons is an absolute measure of an animal’s intelligence, be it a plant eater or a meat eater.
(C)The number of neurons reveals that plant eaters are generally smarter than meat eaters.
(D)The ratio of the number of neurons relative to the size of an animal’s body can indicate how smart the animal is.