机房温度和（）应符合维护技术指标要求，保持正常的通风。
A.温度
B.湿度
C.空气洁净度
D.以上都对
参考答案：B
There is a crowd of people in front of the house over there. What do you suppose
_____ there?
A．is happened
B．has happened
C．happening
D．to have happened
什么是生物反应器？研究和开发生物反应器有何益处？
