—______ did you sleep last night?—Only five hours. I stayed up late to do my homework.

It is usually warm in my hometown in April, but it ________ be rather cold sometimes.

 — Mary, whose photo is it?—It ______ be Lu’s. Those are her parents.

I want to open the door, but it _____ open.

- Tom, where is your father?- I’m not sure. He _______ in his office.