Fifty dollars for such a T-shirt! You _______ be joking!—I’m serious．It’s made of silk.

You’d better not always look up the new words __________ the dictionary while reading. Sometimes we need to guess. [ ]

My grandparents never remember my telephone number, and they always _______ look it up.

How did the accident happen?— You know, it difficult to see the road clearly because it .

You’d better go there by train. The train ticket is __________the airplane ticket.