must have + p.p
表示 曾经一定......
我在书上看到一句是这样子写的
She must have been going very fast before the accident;
the skid marks measure 20 meters.
它为什用 must have been going呢?
它是不是要强调 before the accident 正在做的事情 ?
它能写成 She must have gone very fast before.........吗?