For Years, Your Parents Claimed They Had No Desire to Join

Multiple Choice

For years, your parents claimed they had no desire to join a social web site. Recently, however, they joined one and said they did so because all their relatives have joined the same site with them. Your parents' behavior is an example of

A) a switching cost.
B) a network effect.
C) the impact of positive market feedback.
D) the impact of negative market feedback.