h teachers are supposed ______theirstudents a test in class, even after class, ______better teaching results.

ned cats and dogs this morning. I’mglad we took an umbrella.—Yeah, we would have got wet all over if we ______.

17．The movie is to deucate people about environmental problems ______our planet.

36How can you know whether you will succeed ______ you never try?

Having checked the doors were closed , and _________ all the lights were off, the boy opened the door to his bedroom.