房地产周期循环是指房地产业活动或其投入与产出有相当的波动现象，且此现象重复发生。（）
参考答案：对
—Hello! Could I speak to the headmaster?
—______, Please call back later. [ ]
A. Wait a minute
B. Hold on for a moment
C. Speaking
D. Sorry, he isn't here at the moment
简述3、4号机汽轮机高压遮断模块试验如何作？
