要求再度显示手信号昼、夜间怎样显示？
参考答案：
昼间拢起的手信号旗右臂向右方上下摇动；夜间红色灯光上下摇动。
Our English teacher is ill, and we are all ______ her health.
A．concerned about
B．careful of
C．grateful for
D．calm down
提出位温概念有何意义？
