_____ the rain stops, we' 11 set off for the station.
| A．Before | B．Unless | C．As soon as | D．Though |
--- You won’t go to Mary’s wedding, will you?
--- No, _____ invited．
| A．if | B．once | C．though | D．in case |
According to a UN report, one third of the world population have no ____ to clean drinking water and health care．
| A．means | B．approach | C．channel | D．access |
It is likely that water is not ____ endless resource, nor ____ that can be made once more．
| A．the; / | B．an; one | C．an; that | D．/; one |
How long ______ teaching? Forty years.
| A．he will have been | B．will have he been |
| C．will have been he | D．will he have been |
An operation is usually performed by a ______.
| A．doctor | B．dentist | C．surgeon | D．scientist |