An Analysis of "Virginity Pledges" That Encourage Adolescents to Promise

An analysis of "virginity pledges" that encourage adolescents to promise to abstain from premarital sex has found that:

A) pledging works equally well for adolescents of all ages.
B) pledging has a big effect in schools in which few students take the pledge.
C) pledging works well in schools in which nearly everyone takes the pledge.
D) about 82% of adolescents who take a virginity pledge will deny having done so five years later.