1 Police estimate that only 1 to 2 percent of hitchhiking crimes are reported, so there are no accurate statistics on such events. 2 But frequent horror stories indicate that hitchhiking can be dangerous to both hitchhiker and driver. 3 There was the nineteen-year-old woman who accepted a lift from three young men in New Jersey, expecting a ride across the bridge to New York City. 4 Instead they drove to a motel, where they repeatedly raped her. 5 Luckily, she escaped with her life. 6 Less fortunate was the eighteen-year-old woman student who disappeared from campus after accepting a ride with a stranger and whose decomposed body was found in a suburban sewage plant two years later. 7 Male hitchhikers are less open to assault, but a number of incidents show that they are far from immune. 8 Hitchhikers also face the hazards of riding with an intoxicated or stoned driver, not the least of which is an accident. 9 They also risk assault or robbery by other hitchhikers and being stranded in out-of-the-way places. 10 Drivers, too, are subject to assault and robbery. 11 And they risk accident by stopping on a busy highway, or arrest if their passengers happen to be carrying drugs. 12 Some male drivers have picked up young girls who threatened to call the police and cry rape unless the men handed over all their money. The main idea is sentence____. ( 请写出句子的序号,例如: 1)