It was 80 years before Christopher Columbus crossed the Atlantic _____ Zheng sailed to East Africa 为什么选that？
如果去掉It was 和that 变成这个Zhenghe sailed to East Africa 80 years before Christopher Columbus crossed the Atlantic. 为什么还完整？
80 years before Christopher Columbus crossed the Atlantic.做什么成分。。。
我真的无法了，网上求助各种无效。。。
如果去掉It was 和that 变成这个Zhenghe sailed to East Africa 80 years before Christopher Columbus crossed the Atlantic. 为什么还完整？
80 years before Christopher Columbus crossed the Atlantic.做什么成分。。。
我真的无法了，网上求助各种无效。。。
