1. The zookeeper wrote a letter to the Chinese ___________(政府)
2. We all know the _________(重要性) of learning English well.
3. You should (积极地)take action to stop the pollution.
4. I will （归还）the book to the school library as soon as possible.
5. Zhalong is one of the world’s most important ___________ (湿地).
6. （燕子）fly to northern countries in summer.
