SHOULD
1. I know that it was wrong from me to upset Mark
I know that I ........................ Mark upset
POSSIBLY
2. There is no way that my sister wrote this letter
This letter ........................ by my sister
PREVENTED
3. Because of the snow we could not get to the gig
The ........................ the gig
ROUND
4. I have been too busy to watch the movie you sent, but I will do it soon
I ........................ the movie you sent, but I will do it soon
NOT
5. Peter's card never arrived, so it's possible he forgot to post it
Peter ........................ the card, because it never arrived
SUPPOSED
6. They didn't fix the computer problem, even though they said they would
They ........................ the computer working again but they did not
