Sometimes the boy is a bad-tempered child, but he ____ be quite lovely when he wishes．

—Is Nick coming by train?—He should, but he ________ not. He likes driving his car.

 Sorry I’m late. I ____ have turned off the alarm clock and gone back to sleep again. 

 —Look at the boy running on the ground. Is it David?—It      be him. I saw him go to the teacher’s office just now.

She __________ be here. I saw her come in.