英语疑问,求大虾们解释

问题描述:

英语疑问,求大虾们解释
While a young man,he was very ambitious.
教材上解释的是:while用作连词,为省略句,因而是正确的.请问,是省略了那一部分?

原文应是
While he was a young man, he was very ambitious.