As he reached _____ back door, Jack saw _____ strange sight.
| A．the ; / | B．a; the | C．/; a | D．the ; a |
It’s not easy to change habits，________with awareness and selfcontrol，it is possible.
| A．for | B．or |
| C．but | D．so |
Don’t turn off the computer before closing all programs，________you could have problems.
| A．or | B．and |
| C．but | D．so |
I was glad to meet Jenny again，________I didn’t want to spend all day with her.
| A．but | B．and |
| C．so | D．or |
There’s no way of knowing why one man makes an important discovery________another man，also intelligent，fails.
| A．since | B．if |
| C．as | D．while |
I have heard a lot of good things about you________I came back from abroad.
| A．since | B．until |
| C．before | D．when |