报关员代表所属单位向海关办理报关业务时，只能担任其所属报关单位的报关工作。

用导线连接电路元件时，要将导线的两端接在电池盒、灯座、开关等的______上，并且按______时针旋紧，保证接触良好．

Waste paper shouldn't ______ everywhere. It's our duty to keep our classroom clean. [ ]

A. be thrown

B. throw

C. is thrown

D. are thrown

齐明点

—You wants ______ sandwich
—Yes, I usually eat a lot when I'm hungry.

A．another


B．other
C．others



D．the other

曲柄连杆机构主要是由（）和（）及（）三部分组成。