人字桅杆的两脚间应有连接绳，防止桅杆脚受力时向外滑移。
参考答案：对
The firemen ____the fire as soon as they got to burning buildings.
A．put up
B．put away
C．put out
D．put down
在安装止回阀的阀盖与阀体之前，应在阀盖与阀体之间安装（），保证其密封可靠。
A.四氟带
B.麻绳
C.密封垫片
D.橡胶圈
