单选题 .  (英语专业必做)
    Drunken driving—sometimes called America's socially accepted form of murder—has become a national epidemic. Every hour of every day about three Americans on average are killed by drunken drivers, adding up to an incredible 250,000 over the past decade.
    Heavy drinking used to be an acceptable part of the American macho (男子汉) image and judges were lenient in most courts, but the drunken slaughter has recently caused so many well-publicized tragedies, especially involving your children, that public opinion is no longer so tolerant.
    Twenty states have raised the legal drinking age to 21, reversing a trend in the 1960s to reduce it to 18. After New Jersey lowered it to 18, the number of people killed by 18—20-year-old drivers more than doubled, so the state recently upped it back to 21.
    Reformers, however, tear raising the drinking age will have little effect unless accompanied by educational programs to help young people to develop "responsible attitude" about drinking and teach them to resist peer pleasure to drink.
    New laws have led to increased arrests and tests in many areas already, to a marked decline in fatalities. Some states are also penalizing bars for serving customers too many drinks. A tavern (酒栈) in Massachusetts was fined for serving six or more brandies to a customer who was "obviously intoxicated" and later drove off the road, killing a nine-year-old boy.
    As the fatalities continue to occur daily in every state, some Americans are even beginning to think well of the 13 years of national prohibition of alcohol that began in 1919, which President Hoover called the "noble experiment". They forgot that legal prohibition didn't stop drinking, but encouraged political corruption and organized crime. As with the becoming drug trade, there is no easy solution.6.  Drunken driving has become a serious problem in America because ______.