(1) know
(2) what
(3) subjects
(4) written
(5) many
(6) to
(7) understanding
(8) friendship
IX.
1. It is high time we went home
2. Unless you have a jacket and tie, you can’t go into this restaurant
3. It was such a difficult question that no one could answer it
4. This letter hasn't been finished yet.
5. If he is good at English, he can get a job.