— I phoned you at 7 yesterday evening but nobody answered.
— Oh, I ________ my dog in the park then.
| A．walked | B．was walking | C．had walked | D．would walk |
This photo of mine was taken __________ stood the famous twin-tower before the 9.11 event.
| A．which | B．in which | C．where | D．there |
Though they met for the first time, they talked __________ they were good friends.
| A．even if | B．as if | C．even though | D．if only |
The medicine works more effectively __________ you drink some hot water after taking it.
| A．as | B．until | C．although | D．if |
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 |