Don’t leave your seat ________ all the papers have been collected by the teacher.

–What do you think of Henan Province? --It’s a wonder place. ____ you go there, you can find many fantastic sights. 

I never know this         he tells me.

________my mother is very tired after a whole day’s hard work, she tries to spare time for me.

Although we are young, ______ we can still do something to help them.