用括号内所给单词的适当形式填空。
1. Let's ________ (study) for our country.
2. Today is sunny. Why not ________ (go)fishing?
3. There is enough _____ (water) in the bottle.
4. Which language is ________ (easy), English or Japanese?
5. Shanghai is one of the biggest ________ (city) in the world.