⏪ 新概念英语 - [4-008] - (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 makes trading between rich countries difficult? 什么使得富裕国家之间的贸易变得困难？Trading standards 📁 请先导入本地文件， 需要帮助？点击我 ↗