What element is key to establishing a strong purpose

Which number is main idea? i need this quick. 5. (1) preventing, not treating, social problems is the goal of an increasing number of programs. (2) by teaching teenagers to resist peer pressure, for example, one program them avoid serious problems with drinking and drugs. (3) in another program, nurses taught poor, young, pregnant women all the basics of good child care. (4) these young mothers then gave better care to their babies than mothers who did not receive such training. (5) a third program paired at-risk teenagers with adults from the community. (6) each adult agreed to meet with the teenager on a regular basis through all four years of high school. (7) the result was that none of the teenagers dropped out of high schools in which the average dropout rate was close to 50 percent. (8) instead, almost all of the teenagers went on to college.