人体对机械振动的反应取决于（）。
A.振动的频率
B.振动作用的方向
C.人的心理状态
D.暴露时间
E.振动的强度
参考答案：A, B, C, D, E
在△ABC中，D、E、F分别是AB、BC、AC的中点，若△ABC的周长为30cm，则 △DCE的周长为（ ）
句型转换。
1. My mother said to me, "Don't go alone at night." (改为简单句)
My mother told me _____ _____ go alone at night.
2. The Browns came to China in 1997.(对划线部分提问)
_____ _____ the Browns to China?
3. Mr. Fat has few good friends. (改为反意疑问句)
Mr. Fat has few good friends, _____ _____?
4. My home is about twenty minutes by bike. (改为同义句)
It _____ me twenty minutes _____ _____ there from my house by bike.
5. It's a good idea.(改为感叹句)
How _____ _____ _____ is!
