What percent of the United States population is over age 65?

What is the name of the stress hormone that has been linked to differences in behavior of children in day care versus children reared exclusively at home?

A) Thyroxine B) Cortisol C) Testosterone D) Estrogen

Which of the following seems to be even more important in older age as a contributor to longevity and good health?

A) Relationship status B) Exercise C) Recreational activities D) Social networks