John promised his doctor he ________ not smoke, and he has smoked ever since.
| A．might | B．should | C．could | D．Would. |
It will be a long time __________ we finally solve the problem of pollution.
| A．before | B．since | C．when | D．Until |
It was five o'clock in the afternoon __________ they climbed up to the top of the mountain.
| A．since | B．when | C．that | D．until |
—Did you remember to give Tom the book you borrowed from him?
—Yes, I gave it to him __________ I saw him.
| A．while | B．the moment | C．as | D．once |
Busy __________ she is, Rita sets aside two hours every Sunday afternoon to spend with her son.
| A．although | B．as | C．while | D．even if |
Mr. Brown arranged for the taxi to come at six __________ he would not have to wait long at the station.
| A．so that | B．even if | C．before | D．because |