Question

Mr. Smith isn’t here yet. I think he ______ about the meeting

Mr. Smith isn’t here yet. I think he ______ about the meeting.
A. should have forgot B. ought to forget
C. must have forgot D. may not forget
选A不可以吗？

Answer 1

这里所说的here应该指的是会议现场，所以表示比较肯定的推测，用must比should更能表示这个意思。
must +不定式完成式（have done）
用于肯定句中，表示对过去行为的推测。意为“一定、想必”。
1. You must have seen the film Titanic.
2. He must have been to Shanghai.
4）should +不定式完成式（have done）
用于肯定句中，表示对过去行为的推测。
He should have finished the work by now。
表示“本应该做而实际上没有做某事”，其否定式表示某种行为本不该发生却发生了。可以与ought to +不定式完成式（have done）互换。
1. You ought to / should have helped him. (but you didn’t.)
2. She shouldn’t have taken away my measuring tape, for I wanted to use it.

Answer 2

A不行，因为它是虚拟语态，而think的从句是不会用虚拟语态的。
答案是哪个？