Key to the exercises:

1).

1.thought  2. surprising  3.differences  4. mainly  5. or 

6. Generally  7. follow  8. sounds  9. Canadians  10. rest

2).

1. knocked  2. must  3. breathing  4. side  5. Leave

6. hurt   7. stay    8. happened  9. easy  10. called

3)

1.bought   2. ran  3. possibly  4. back  5. foolish

6. following  7. either  8. fault  9. true  10. insist