为什么停采煤机时要先停电后停水？
参考答案：
停止采煤机时先停水后停电，易造成采煤机过热而损坏。
There are hundreds of visitors _____ in front of the Art Gallery to have a look at Van Gogh's paintings. [ ]
A. waited
B. to wait
C. waiting
D. wait
引起该患者感染最主要的原因是
A．白血病细胞浸润B．联合化疗C．皮质激素的应用D．代谢亢进E．成熟粒细胞减少
