——Hi, Mike．Any idea where Mary is? ——She ____ in the classroom．I saw her there just now.

—The contest is so easy, but you fail to pass it．—I’m sorry it ______ be this way．

—Did you meet with the famous space hero , Yang Liwei ?—        I had come here earlier !

Since nobody gave him any help, he    have done the research on his own.

 Robert wishes that he ________ business instead of history when he was in university.