The fans cried as soon as they saw the movie star.The fans cried as soon as they saw the movie star.=The fans had no sooner seen the movie star than they cried.为什么转变后的句子要用过去完成时?

问题描述:

The fans cried as soon as they saw the movie star.
The fans cried as soon as they saw the movie star.=The fans had no sooner seen the movie star than they cried.
为什么转变后的句子要用过去完成时?