Some frightening pets _________ be kept home so that they won’t hurt others.

The boss has given everyone a special holiday, so we ________ go to work tomorrow.  

One of our rules is that every student_____wear the school uniform while at school．

 ------What kind of house do you want to have? Something big ? ------Well, it _______ be big.—That’s not important.

 A mistake ______ have been made on our bill. We didn’t order any fish today.