操作平台护栏扶手的最小高度应为（）
A、0.9米
B、1米
C、1.1米
参考答案：C
Questions 1-4
Why did people put up the slogan "save the whales"？（）
A．They think whales are their friends.
B．They believe whales can save humans.
C．They wanted to ban whale-hunting.
D．They enjoy watching whales in an aquarium.
锅炉除灰应（）进行。
A.每天定时
B.在排烟温度明显升高时
C.在送风机风压明显增高时
D.B或C
