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 significant positive effect, even in schools in which few students take the pledge.
C) pledging works well in schools in which nearly everyone takes the pledge.
D) a large majority of adolescents who take a virginity pledge will deny having done so five years later.