高硅铸铁作管道只能用（）连接。
A.活套法兰
B.螺纹
C.插套
D.焊接
参考答案：A
阅读对话，完成句子。
John: Hello.
Bill: Hello. It's Uncle Bill. Is everybody at home?
John: Yes.
Bill: What are they doing?
John: Grandma is writing. Dad is writing an e-mail. Mom is washing the clothes. And I am sweeping the floor.
1. _______________ is _________________________.
2. _______________ is _________________________.
一个国家或地区在一定时期内对进口贸易和出口贸易所实行的政策称为( )。
A．自由贸易政策B．保护贸易政策C．国际贸易政策D．国内贸易政策
_______________ is _________________________.
_______________ is _________________________.