After the new technique was introduced， the factory produced _______ tractors in

I like the teacher__________classes are very interesting and creative.

That is ________ interesting work.

There’s somebody at the door. Who ____ it be? Is it the postman? — No. It ______ be him. It’s just seven o’clock. It’s too early.

Mind your steps, guy! Don’t you see the words “_______ the grass”?—I’m sorry.