第3题: [单项选择]带传动是以传动带作为中间挠性件来传递运动和动力的。下述对带传动特点描述错误的是( )。 A. 运动平稳无噪声,可以缓冲冲击和吸收振动 B. 结构简单,传递距离远 C. 制造和安装简单,维护方便,不需润滑 D. 外廓尺寸大,效率较低,但传动带寿命长,且传动精度高 参考答案:D 答案解析:[解析] 传动带寿命较短,传动精度不高。D项中的说法相反,故是错误的。
第9题: [单项选择]Why didn’t Alice go to bed until late at night A. She was doing her housework. B. She was working hard at her lessons. C. She was watching TV. 参考答案:B 答案解析:[听力原文] M: Hello, Alice. You look tired today. W: Yes. I stayed up too late last night. I was