When I was a child, I ______ watch TV whenever I wanted to.
We should work together to build a society for kids, ________free from war and violence.
He slipped(溜进) into the classroom without ___________.
This special strain of rice makes _________ possible to produce one third more of the crop in the same fields.
---Is that the small town you often talk about?---Right, just the one ______________ you know I used to work for three years.
Although the first part of the book is easy, the rest ______.