阅读理解。阅读下列短文, 从给的四个选项 (A、B、C和D) 中, 选出最佳选项。
【2014·山东济宁模拟】
An alcohol breath test (ABT) is often used by the police to find out whether a person is drunk while driving.In the United States，the legal blood alcohol limit is 0.08% for people aged 21 years or older，while people under 21 are not allowed to drive a car with any level of alcohol in their body.
