正确答案为选项D ,其录音对应内容在第一句与最后一句，即美国政府1968 年以前都没有要求车辆配备座椅安全带，配备气囊直到1998年才成为强制性要求。 选项A 错在虽然说对了 1968年要求车辆配备座椅安全带的时间，但却把小汽车常见配有气囊的时间说成了强制配备气囊的时间。选项B 说的是美国政府通过法律要求乘车人（occupants)系安全带的时间和气囊开始常见的时间。选项C 说的 1984 与选项B 犯了同样错误。

[重点难点]
理解mandatory与 compulsory之间的语义关联，在此前提下抓住时间。

[录音原文]
The U.S. government did not require vehicles to be fitted with seat belts until 1968. And it was not until 1984 that the federal government passed a law requiring occupants to buckle up. Similarly, airbags were not available in some GM and Ford models in the 1970s, and were not common to all cars until 1991; they were not mandatory in the U.S. until 1998.