1. If you do not buy coffee...
2. ..., he will certainly come to our party.
3. ... if he had not hurt his leg.
4. If my friend worked in my office, ....
5. ..., you would improve your language skills.
6. ..., your mother will be happy.
7. If she had returned earlier, ....
8. ..., I would buy them.
9. If you ring me up, ....
10. If you were a poet, ....
11. ..., he wouldn't know English literature so well.