Many people believe we are heading for environmental disaster _____ we basically change the way we live.
| A．but | B．although | C．unless | D．once |
I would appreciate it _______ you call back this afternoon for the appointment.
| A．until | B．if | C．when | D．that |
. This tower _______ back to 1860s and it is still in good condition.
| A．is dating | B．dated | C．was dated | D．dates |
You can see the stars on a clear night, but in the daytime they are __________.
| A．unbelievable | B．invisible | C．inaccessible | D．unavailable |
Finding her car stolen, __________.
| A．a policeman was asked to help | B．the area was searched thoroughly |
| C．it was looked for everywhere | D．she hurried to a policeman for help |
We would not __________ such hard work. It’s impossible for us to complete it in such a short time.
| A．take in | B．take off | C．take on | D．take down |