I selected #4 for the following reasons:
If you do #1, you will continue to have illegal abortions. Moreover, the law of the land follows the culture of the land. Thus, before the law can be changed, the culture has to change.
If you do #2, you will continue to have abortions of convenience (as opposed to abortions due to the specter of not having enough money to raise a(nother) child).
If you do #3, you will continue to have abortions for unplanned pregnancies (within marriages). As long as people continue to see abortion as a viable option, it will continue to occur.
If you do #4, then regardless of the law, regardless of the economic situation of the pregnancy, and regardless of whether the child was conceived morally or immorally, the abortion won’t happen. In the past, this was true. Out of wedlock, the father might step up and do the right thing. Not enough money, the child might have been given up for adoption. Abortion would have been the last thing to be considered, and only in the most desperate of situations.
In the end, changing the culture will change everything else; economics, law, and sexual morality. Going for 1, 2 or 3 will be less-lasting solutions than 4.