⏪ 新概念英语 - [4-018] - (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 would you say is the main characteristic of porpoises? 你认为海豚的主要特征是什么？Porpoises 📁 请先导入本地文件， 需要帮助？点击我 ↗