Underline the correct verb form:
1. $100 was/were too much for the jacket.
2. Many foods contain/contains traces of nuts.
3. The United States is/are a big country.
4. Those trousers really suit/suits you.
5. Chicken pox is/are a common childhood illness.
6. Physics do/does not interest me that much.
7. My hair is/are growing very quickly at the moment.
8. The world’s population is/are growing rapidly.