The change in the shape of the lens in order to focus on a visual image is known as _______________

Which of the following terms would be the best description of the relationship between the nervous and the endocrine systems?

a) interdependent b) independent c) dependent d) unidirectional

Researchers randomly assigned adolescents to either a single-grade classroom or a mixed-age classroom. This is an example of a

A) naturalistic observation. B) case study. C) natural experiment. D) field experiment.