________ theory would be most likely to mention such factors as social approval and increased self-worth as motivations for prosocial behavior

Which of the following factors influences the rates of DZ twinning?

A) ethnicity B) a history of DZ twins on the mother's side of the family C) maternal age D) all of the above

Alana feels that the fact that her best friend borrows her notes from class, is always running late, and sometimes doesn't laugh at her jokes, is made up for by the fact that she is always willing to listen, always lets Alana borrow her CD's,

and gives her rides everywhere. Alana feels there is ________ in the relationship. A) social exchange B) equity C) a reinforcement-affect effect D) communality