—Why are those people gathering in the middle of the street?—I don’t know. There ________ be an accident.

 —Tom is in low spirits today. He ______ again in the job interview.—What a pity! He has been greeted with bad luck these days.

The lady ________ have done something wrong, because she is looking guilty.

--Is the man standing outside the teacher’s office Mr. Zhou?  --No, it ______ be him. He has gone to Hong Kong for an academic conference. 

Rose, you       leave your school things on the floor like this. Keep your room clean and tidy.