— Look at the boy playing basketball on the ground. Is it George?— It ________ be him. He told me he would play basketball after class, but he’s not sure.

—It's the office！So you ________ know eating is not allowed here.—Oh，sorry.

He ________ to swim when he was five.

 — Shall I tell John about it ?— No , you         . I’ve told him already .

The World Wide Web is sometimes jokingly called the World Wide Wait because it ______ be very slow.