natural speaking - similar to native speaker
- pronunciation
- intonation （语调)
- enunciation(发音清晰)
- slangs: wanna, gonna
- idioms:
- self-correction: sorry, what I meant to say was...
coherent （连贯性）
- answer the questions accurately
- stay on topic
- give a complete and clear answer that is easy to understand
complex
- 使用从句
- 高级语法：现在完成时，过去完成时，被动语态， 进行时等
