Controlling water-pollution is necessary_____ it will be expensive.

Such a person _____ you talked about is seldom seen now.

 _______ the teacher’s instruction in the lab_____ important.

This is the very information _______ we can learn what is selling best in the market. .

 All _____ can be done has already been done.

The girl ______in red is a successful writer, who _______ Tom last month.

 Mr. Smith doesn’t believe that his daughter can work out the problem that easily,_____?

 It is said that Tom hasn’t passed the driving test, but, ______ he is a little too young.

She_____ have gone to Shanghai for a visit. She has been discussing the papers with me for a whole day.

-----I’m taking my TOEFL examination next week.

-----______!