1. I have done such a difficult exercise.
This is the.............................................
2. John finished his essay in two hours.
It.............................................................
3. My knowledge of computer is very poor.
I know very..............................................
4. I walkked home inheavy rain.
When I.......................................................
5. My friend couldn't finish his assignments because he was tired.
Because of......................................................
6. The test was too difficult for the students to do.
It was.......................................................
7. I haven't visited Singapore since 2000.
The last time......................................................