I. Choose the best answer to complete each of the following sentences.
1. There are two main kinds of sports: team sports and ____ sport s.
A. individual B. separate C. competitive D. popular
2. Football is the ___ sport in the world. It is considered “the king sport”.
A. more popular B. popularer C. most popular D. populares
3. It is ______ to skate there because the lake has just been frozen.
A. dangerous B. safe C. popular D. interesting
4. This river is not ______ enough for children to swim in.
A. clear B. clean C. polluted D. cold