1.I was about to leave my house_____there was a knock at the door.
  A. while     B. as     C. when     D. and
2.Hardly_____my mail box when I found an E-mail from my teacher.
  A. I had clicked     B. had I clicked    
  C. did click     D. I clicked
3.No sooner_____he realized that the left the key in the room.
  A. had Tom locked door than     B. had Tom locked the door than
  C. had Tom locked the door when     D. Tom locked the door than
4.He was so interested in the Vedio game that it was midnight_____he realized it.
  A. since     B. before     C. until     D. as
5.It’s a long time since I enjoyed myself. The sentence means_____.
  A. I enjoyed myself for a long time 
  B. I haven’t enjoyed myself for a long time
  C. I want to enjoy myself 
  D. want a long time after I enjoyed myself
6. It seemed only seconds_____the boy finished his homework.
   A. when     B. ill     C. after     D. before