联合行文时，作者应是( )。
A．上级机关
B．同级机关
C．层次级别较高的主管部门或机关
D．主送机关
参考答案：B
用所给动词的适当形式填空。
1. The sweater ______ (be) $15.
2. It's five. Let's ______ (play) football.
3. Mum, I want ______ (have) a party this evening.
4. She ______ (have) a computer game.
5. There ______ (be) a book and two pencil cases on the desk.
螺旋、偏心、凸轮等机构是斜楔夹紧的变化应用。( )
