A(n) ________ experiment may use animals as subjects in order to learn more about human beings.

Mice without the gene that produces this hormone (question 28) or its receptors were unable to control their food intake or to maintain a normal body weight.

a. true b. false

Marwan understands that when a ball of clay is flattened into a pancake shape that there's still the same amount of clay. He says, "you could just bunch up the clay into a ball again—it's still the same thing." He is exhibiting:

A) conservation. B) identity. C) reversibility. D) all of the above