—What are your parents?
—My father is a teacher, and my mother is______.

The chairman thought _____ necessary to invite Professor Smith to speak at the meeting.

---- What about the two MP3s? 
---- Sorry, but I don’t like _____ of them. Would you please show me a third one?

They form a polar molecule, ____ is, ____ with a slightly positive end and a slightly negative end.

The dentist would prefer ___ if you could come a little earlier tomorrow.

The chairman thought _____ necessary to invite Professor Smith to speak at the meeting.

____ is up to us to give them all the help _____ we can.

It has been a long time for human to make _____ to reach the moon.

My parents always remind me to work hard at my lessons and I am forbidden to do_________except studying.

Your story is perfect.I have never heard______before.