下列()溶剂有毒性。
A、甲苯
B、甲醛
C、丙酮
D、以上都对
参考答案:D
什么叫电泵井?电泵井是如何将井液举升到地面的?
All the lights _____ and we were _____ in the dark. [ ]
A. turned off; keeping
B. went out; left
C. went out; keeping
D. turned out; left