High schools should only teach abstinence. Students who practice abstinence will never experience an unplanned pregnancy or contract a sexually-transmitted disease. Each of the following weakens the argument EXCEPT: ['Religious organizations support the teaching of abstinence.', 'Students are less likely to follow teaching about abstinence than safe sex.', 'Failing to teach about contraceptives increases the spread of sexually-transmitted diseases.', 'The percentage of students engaging in abstinence is lowest in school districts that only teach abstinence.']