___in doing so,created work pants for the cowboys of...空格填什么?

题目

___in doing so,created work pants for the cowboys of...空格填什么?
Twenty years later,he made the first pair of blue jeans,____in doing so,created work pants for the cowboys of the wild American West.
语法填空,in前的空格要填什么?

答案

Twenty years later,he made the first pair of blue jeans,___who__in doing so,created work pants for the cowboys of the wild American West.who在这里指he而which只能指物不能指人.