老师：你好！
Then the Dean and the committee came back, “Gentlemen”, the Dean said, “the candidate we have chosen is Mr. Hobdell.” Uncle Theo had won. You could have knocked him down with a feather. The audience were completely taken by surprise, and the Dean continued, “ I think I ought to tell you how we arrived at the decision. We were all filled with admiration at the learning and eloquence of Mr. Adams. I was greatly impressed. I didnt think he had it in him. But, you will remember, Mr. Adams read his lecture to us. When Mr. Hobdell’s turn came, he repeated that speech, word by word from memory, though, of course, he couldn’t have seen a line of it before. Now a fine memory is absolutely necessary for this post; and what a memory Mr. Hobdell must have! This is why we decided that Mr. Hobdell was exactly the man we wanted! ”
文中，“You could have knocked him down with a feather.” 为何要用could have done的形式，可否改用一般过去时You knocked him down with a feather 呢？ 含义有什么不同？
文中，为何要说“ I didnt think he had it in him” 而不说“ I dont think he ...” ? 用I didnt think 和 I dont think 含义句意到底有什么不同？
文中，“he couldn’t have seen a line of it before” 可以换用一般过去时吗？ 这里用couldnt have done表达了讲话者什么含义呢？
文中，“ and what a memory Mr. Hobdell must have! ” 这里must是情态动词，说明讲话者很一定的推断吗？
“You could have knocked him down with a feather.” 中
could have done为虚拟语气，可以觉得省略了一个if虚拟条件从句：if you had tried to do so.
不可改用一般过去时 You knocked him down with a feather ，由于一般过去时表示过去的事实，意思就成了“某人曾用一根羽毛将他击倒了”。
“ I didnt think he had it in him” 这是直接引语中的话，即说话人原来以为亚当先生没学问和口才，听了他的演讲之后才了解原来他这样的才了解事实并不是他以前觉得的那样。
I didnt think : 原以为...不...。I dont think: “he couldn’t have seen a line of it before” couldnt have done在此表示对过去发生的事情的可能性的推断——不可能发生过如此的事。直接用一般过去时，则没推断意义，而表示事实上，某事没发生。
and what a memory Mr. Hobdell must have! ” 这里must是情态动词，表示讲话者很一定的推断，并据此发出感叹。这是一个感叹句。
