题目

People are being lured (引诱)onto Facebook with the promise of a fun, free service without realizing they’re paying for it by giving up toads of personal information. Facebook then attempts to make money by selling their data to advertisers that want to send targeted messages.Most Facebook users don’t realize this is happening. Even if they know what the company is up to, they still have no idea what they’re paying for Face book because people don’t really know what their personal data is worth.The biggest problem, however, is that the company keeps changing the rules. Early汽车行驶的正前方有一座高山，汽车以12m/s 的速度匀速行驶．汽车鸣笛2s后，司机听到回声，则此时汽车距高山有多远？（设声音在空气中的传播速度为340m/s）