⏪ 新概念英语 - [4-023] - (97版) ⏩ ⏳ 正在检测本地文件... First listen and then answer the following question.先听录音，然后回答后面的问题。What are the two main types of bird flight described by the author? 作者描述的鸟类飞行的两种主要类型是什么？Bird flight 📁 请先导入本地文件， 需要帮助？点击我 ↗