Traffic restrictions have come into effect in Beijing ______to improve the capital’s air quality and traffic situation for the 2008 Olympics

下面字母中既是英文字母，又是英文单词的是 。

Thank you for _______my grandpa when I was away .

People who can see with their eyes can’t understand _____ practical use Braille can be of for the blind.

Don’t touch my computer when I’m away, OK–Sorry, .