Which Factor Helps Explain the Historic Low in the Teenage

Which factor helps explain the historic low in the teenage birth rate?

A) The price of condoms has steadily increased.
B) A greater number of adolescents are taking the "virginity pledge" in schools across the country.
C) The rate of sexual intercourse among teenagers has increased,and the use of birth control has decreased.
D) Substitutes for sexual intercourse,such as oral sex,are increasingly accepted as an alternative to sexual intercourse