All birds and mammals sleep

Compared to other Western nations, U.S. teenage pregnancy rates are:

A) higher. B) lower. C) similar. D) lower or higher, depending on the country to which the United States is compared.

A young man is having trouble getting along with his roommate. Sometimes the roommate goes for days without speaking. Other days, the roommate is a nonstop talker, speaks rapidly, and is often abrasive and aggressive. The roommate is showing symptoms suggesting

a. major depression. c. bipolar disorder. b. depression. d. delusional disorder.