That was difficult to build that railroad at that time.单句改错
问题描述:
That was difficult to build that railroad at that time.单句改错
答
It was difficult to build that railroad at that time.
it作形式主语,真正的主语为后面的不定式短语
答
第一个that改成the 或者 直接去掉
答
第一个that 改为 it
答
It was difficult to build that railroad at that time
属于动词不定式作主语