机组正常运行时，润滑油系统的全部耗油是由（）提供。
参考答案：主油泵
独立避雷针的冲击接地电阻一般不应大于（）Ω。
A、0.5
B、1
C、4
D、10
— Hello, I _____ to ask if I can book two tickets for tonight's film.
— Sorry, we've already sold out. [ ]
A. phone
B. will phone
C. am phoning
D. have phoned
