It was _______ he was ill that he didn’t goto school

In our school library there _____ a number of books on science, and in these years the number of them _______ growing larger and larger.

Scientists study ____ human brains work to make computers.

After the 2008 Olympic Games, more and more people in Western countries begin to learn Chinese_____ they can better understand the culture of China.– I’m sure they will.

She________the opportunity，but unfortunately she just let it go.