题目

为了督促司机遵守限速规定，交管部门在公路上设置了固定测速仪。如图所示，汽车向放置在路中的测速仪匀速驶来，测速仪向汽车发出两次超声波信号，第一次发出信号到接收到反射回来的信号用时0.5s，第二次发出信号到接收到反射回来的信号用时0.4s。若测速仪发出两次信号的时间间隔是0.9s，超声波的速度是340m/s，下列说法中正确的是A. 汽车接收到第一次信号时，距测速仪170mB. 汽车两次接收到信号时位置相距34mC. 在该测速区内，汽车的速度是18.9m口语运用（每小题 1分，共 5分）阅读下面对话，从方框内 7 个选项中选择 5 个恰当的句子完成此对话，并将其番号填入题前括号 内。A. How often does he go out?B. Who did he travel with?C. Where is Jim?D. Has he ever been there before?E. When did he go there?F. Has he gone to England?G. How long will he be away?A： Excuse me， Bob. 1. I haven’t seen him for weeks.B： He’s gone to England.A： Really? 2.B： He went there last week.A： 3.B： Yes. He had lived there for ten years before he came to China.A： 4.B： He traveled with his friends.A： 5.B： He’ll be away for about two weeks.A： Oh， thank you. I’ll call him this evening.