28. I’m afraid we’ll have to work extra hours for there are still some problems ________.

You’d better not ride the bicycle on snowy days; you ______ fall．

17．—May I surf the Internet tonight? — No, you ______．You must do the exercises．

everything to go wrong in advance, ________ youmay feel at a loss when it does.

Thank you very much for showing me the way to thestation.— ______.