Every possible means ____, but none ____ successful．
| A．has tried; has proved | B．tried; proves |
| C．has been tried; proves | D．is being tried; is proved |
You should make it a rule to leave things _________ you can find them again.
| A．when | B．where |
| C．then | D．there |
Now he works in the factory _________his father used to work.
| A．where | B．when |
| C．which | D．that |
You should let your children play _________ you can see them.
| A．where | B．when |
| C．in which | D．that |
The school was built _________ there had once been a church.
| A．where | B．when |
| C．in which | D．that |
—Mom, what did the doctor say?
—He advised me to live _________ the air is fresher.
| A．in where | B．in which |
| C．the place where | D．where |