置换通风的重要特点包括（）。
A．通风量小，控制效果好
B．低速、低温送风
C．只在紧急的事故情况下使用
D．室内分区流态
参考答案：B, D
If you want to do well in a examination, you had better get yourself into your best ____just before it. [ ]
A. condition
B. state
C. situation
D. position
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