1. Martin Luther King's speech was so exciting that the audience rose to a_____.
2. Afraid of the nuclear leak, they've spent a large sum of money to fit every room with systems that
    p______ the air and water.
3. Before the invention of aspirin, coffee was once used as a p_____.
4. Biggest doesn't n_____ mean best. Many rich countries are very small, while some big countries are not rich.
5. H_____ medicines have been used in China for thousands of years.
6. Your feet are _____(肿的). You must go to see a doctor.
7. A cough and a fever are usually _____(症状)of a bad cold.
8. How can such a large quantity of knowledge be _____(获得)?
9. He suddenly smiled, _____(露出)a set of amazingly white teeth.
10. The ten most _____(频繁)asked questions are listed below.