It will be a long time __________ we finally solve the problem of pollution.
Research shows that though students benefit from having parents involved at school, _____ happens at home matters much more.
________the letters there are answers written by people who are supposed to know how to solve such problems.
Children are excited about the approach of Christmas, _____ may bring great happiness to them.
_____ a piece of cheese cake my mum prepared---You won’t be disappointed!
Oh, boy, why are you just playing games all day? Can't you find something ______ doing at all?