灭火器B类火灾配置场所的危险等级为严重危险级时，手提式灭火器的最大保护距离为()m。
A．7
B．9
C．10
D．12
参考答案：B
---I really don’t know how to thank you enough.
---___________ .
A．No problem.
B．Think nothing of it.
C．With pleasure.
D．Glad to hear that.
滑动轴承常用材料有哪些？
