that was a long time ago 帮忙分析下句型~,是不是a long time 做表语,ago做time的宾补?

问题描述:

that was a long time ago 帮忙分析下句型~,是不是a long time 做表语,ago做time的宾补?

我觉得应该是a long time 做表语,ago做时间状语,