新概念英语3 17课.里面有句话.是这样的 it has been estimate that the bridge were packed with cars.

题目

新概念英语3 17课.里面有句话.是这样的 it has been estimate that the bridge were packed with cars.
为什么句子中的the bridge要使用were呢?不是使用was?.在这句话前面是有句是they support the cables from which the bridge has been suspended.在这里确实使用了has.

答案

是因为用了猜测（假设）语气吧.例如 I could do better if I were you.(如果我是你我会做得更好.)