求一道高考单选题解释WhenItalkedwithmygrandmaonthephone,shesoundedweak,butbythetimewe.up,hervoicehadbeenfulloflife.空上填的是hung,想知道这句话的翻译以及为什么hungup用一般过去时,hervoicehadbee

Question

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.

Answer 1

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