图书室其顶棚、墙面应采用那种装修材料（）
A、不燃性材料
B、难燃性材料
C、可燃性材料
D、易燃性材料
参考答案：A
Mrs. White became a teacher in 1985. She _____ for twenty years by next summer.
A．will teach
B．would have taught
C．has been teaching
D．will have been teaching
在条件复杂，有触电危险的工作应做到怎样监护？
