Tree after tree went own, cut down by the water, which must have been three metres deep.
"must have + 过去分词"表示对已发生事情的猜测。
在英语中,must,may,can三个情态动词可用来表示对事情的猜测。Must意为"肯定",语气很有把握;may意为"可能"、"也许",语气把握性不大。
两者常用在肯定句中。Can意为"肯定"、"也许",常用在否定句或疑问句中。
Must,may,can三者用于表示猜测时,其后面可跟三种不同的动词形式:
3)跟have done表示对已经发生的事情的猜测。例如:
Helen is Lucy’s good friend. She must know Lucy’s e-mail.
We can hear loud voices in the meeting room. They must be quarrelling.
I met Jeff at the gate a moment ago. He can’t have gone to Australia.