— Did you see the boys yesterday afternoon? — Yes. I saw them ________ the fence when I passed.

I really like this song as it is often heard _________everywhere in China.

—What do you think of the book? —Oh , excellent. It’s worth ______a second time.

Which material can be thrown into the sea ________ on the nature of the material?

Anyone ________ bags, boxes, or whatever, was stopped by the police．