6. Measures have been taken to prevent accidents, but much ______ for more improvement.
| A．remains to be done | B．is remained to do |
| C．remains to do | D．is remained to be done |
I would rather buy a house in the countryside than in the city.
| A．it | B．one | C．this | D．that |
Many of the creatures in the movie “Avatar” are not real, but much of __________ happens is attractive.
| A．which | B．that | C．what | D．them |
. —It’s hard to believe that Jack ________ have fought with the policeman.
—Yes. If one ________ ask for trouble, it can’t be helped.
| A．would; will | B．must; may | C．should; must | D．need; dare |
If our car had not ________, we would have been here on time.
| A．broken out | B．broken into | C．broken away | D．broken down |
This new kind of chemicals will help keep the air, soil and water________ from pollution.
| A．free | B．empty | C．loose | D．short |