In Western cultures, friendships tend to be freely chosen and voluntary

What proportion of adults over the age of 65 do no volunteer work?

1/2 1/4 3/4 1/3

Luke's parents are concerned about him because, beginning at about age 2, he began to show little affection toward other people, his speech became very limited to the point where he seldom talked, and he began to engage in repetitive behavior,

such as spinning his crayons and rocking back and forth. If you were to guess what Luke's diagnosis might be, the best choice would be: a. attention deficit hyperactivity disorder b. childhood depression c. autism d. child-onset schizophrenia