— I am going to the dentist at 4 o'clock and it is 3：30 now.— Well, if you ______ leave earlier today, please ask the director for permission.

---There’s someone knocking on the door. Who _________ it be?---It must be John. He promised to be here at 8:00.

--- Whose comic book is it?  --- It ________ be Daniel’s. He often shares his comic books with his friends.

We can hardly believe such a young boy ______ travel around the world all by himself.

—Why didn’t Sam attend the party yesterday evening?—He ___ not have wanted to see me.