this is a brief description of the most significant events in the 250 years during which the fur trade flourished. 4545
问题描述：
this is a brief description of the most significant events in the 250 years during which the fur trade flourished. 4545 什么意思?.
答
this is a brief description of the most significant events in the 250 years (during which the fur trade flourished).
后面是一个定语从句
【这(或以下)是皮毛贸易兴盛的250年来内的重大事件简述.】