You can go out, _________you promise to be back before 11 o'clock.
| A．as far as | B．so far as | C．when | D．so long as |
I failed in the final examination last term and only then __________ the importance of study.
| A．I realized | B．I had realized |
| C．had I realized | D．did I realize |
Only when your identity has been checked __________.
| A．you are allowed in | B．you will be allowed in |
| C．will you allow in | D．will you be allowed in |
The old couple have been married for 40 years and never once __________ with each other.
| A．they had quarreled | B．they have quarreled |
| C．have they quarreled | D．had they quarreled |
Only after my friend came __________.
| A．did the computer repair | B．he repaired the computer |
| C．was the computer repaired | D．the computer was repaired |
I have been living in the United States for twenty years, but seldom __________ so lonely as now.
| A．have I felt | B．I had felt | C．I have felt | D．had I felt |