–Little boy, don’t play with the knife, __________ you’ll cut your hand.  –Sorry, I won’t.

The thing that matters is not whether you fail or not, ________ whether you try or not.

---_______do you send e-mails to your pen friend?  ------Once a month.

_______ everyone is here, let’s begin our meeting.

— Could we practice playing the guitar in the hall, Sir ?                  —No , ___________ you have the principal’s (校长) note.