It’s a secret between us. Don’t tell anybody. —Sure, ______________.

It is said that friends are similar to one another.

______ be Mr．Johnson who is in the office．— No, it _______ be him．I saw him off at the airporthalf an hour ago．

to scientific research, we now have a goodunderstanding of ______ an earthquake is and why it happens

When Peter speaks in public, he always has trouble _ the right things to say.