— Who _____ be phoning us at this time of night? — It might be your sister. 

—You will never believe that it took us two hours to get to the restaurant.—Really? You ________ in a traffic jam.

(2013·安徽高考)It ________ be the vocabulary that caused you the problem in the exercise because you know a lot of words.

These books______very interesting. Many children like reading them.

There ________ be any difficulty about passing the road test since you have practised a lot in the driving school.