In a 1976 Study, Kunz and Woolcott Sent Christmas Cards

In a 1976 study, Kunz and Woolcott sent Christmas cards to a sample of complete strangers. According to the rule of reciprocation, what would we expect the majority of the recipients to do?

A) Send a Christmas card to the researchers.
B) Contact the researchers to find out who sent the card.
C) Return the card to the researchers, since it must have been misaddressed.
D) Throw out the cards and not send anything to the researchers.