求一道高考单选题解释

问题描述:

求一道高考单选题解释
When I talked with my grandma on the phone,she sounded weak,but by the time we .up,her voice had been full of life.
空上填的是hung,想知道这句话的翻译以及为什么hung up用一般过去时,her voice had been full of life用过去完成时.

当我与我奶奶通话时,她听起来很虚弱,但在我们即将挂断电话时,她的声音顿时已充满活力.
by the time是完成时的标志,但by the time后加过去时,主句才用完成时by the time后加过去时,主句用完成时这时by the time表示“到……时候为止”,而不表示“当……时候”麻烦解释你要硬用为止翻译会稍显不符合汉语习惯,by the time指的就是,在某个时间点前,如果死抠翻译,会非常别扭