When we practice_____English,we often end up___in Chinese.

如下图所示是某小组研究浮力问题的装置图，请根据图示回答下面的问题

根据句意用所给单词的适当形式填空。

Everyone should behave ____  in public. (polite)

 --Who's that boy standing over there?  --Sam, a foreign friend of____ . (I) 

After working all night, Kate couldn't stay____ the next morning. (wake)

The UK is an old ____ country, where there are many palaces and castles. (Europe)

Nothing would prevent UNICEF, an international charity,____ the living standards of the children in poor areas. (raise)

下列光现象中，由于光的折射引起的是（　　）