What does a CT scan use x-rays to measure?

A paper written by Alfred Wallace caused Darwin to

a. realize that his theory of natural selection was correct. b. doubt his theory. c. redouble his efforts to collect specimens in support of his theory. d. publish his theory sooner than otherwise would have occurred. e. understand that natural selection applied to all species except humans.

What is the estimated prevalence of major depressive disorder in preschoolers?

a) .05% b) .25% c) 1% d) 2.5%