情態(tài)動詞+動詞完成時,即情態(tài)動詞+have+done.表示對過去的行為或動作進行推測,評論或者判斷.
1.must have done.
表示對過去某事的肯定猜測,其否定或疑問形式都用can/could來表示.
例如：since the road is wet,it must have rained last night.
2；當然對現(xiàn)在發(fā)生或者將來發(fā)生的事情,要用must do表示猜測,否定為can’t do
he must understand that we mean business.
you must be hungry after a long walk.
反意疑問句中含有Must的情況主要有以下幾種：
1）作為情態(tài)動詞表“必須”,這時反意疑問句直接用mustn'/needn't
2)當must表示推測時又分以下幾種情況：
a：對現(xiàn)在事實的推測,反意疑問句與must后面的動詞呼應,如:
You must be joking,aren't you
b:對過去事實的推測,表示動作的時候用did 當助動詞,表示狀態(tài)時用was,如：
Mr Green must have been punished for his being rude at the meeting,didn‘t he (格林先生一定因為昨天在會上魯莽的行為被處罰了,是嗎?） 被處罰表示一個動作
She must have been a policeman ,wasn't she （她過去一定是個警察,是嗎?） 是警察表示一種狀態(tài)
對現(xiàn)在情況的推測,問句部分用主動詞（do,be)一般現(xiàn)在時的適當形式.若是現(xiàn)在進行時,問句部分用現(xiàn)在進行時的適當形式表示.若是there be結(jié)構(gòu),問句用isn't/aren't there.如：
1)He must be there,isn't he?
2)He must have a big family,doesn't he?
3)He must be waiting outside,isn't he?
4)There must be some students in the room,aren't there?
對已發(fā)生的過去情況的推測,若陳述句謂語部分有“must have done”,而且有表示過去的時間狀語,問句部分用didn't；若沒有表示過去的時間狀語,問句部分用haven't或hasn't.如：
1)They must have gone there last night,didn't they?
2)They must have arrived by now,haven't they?（根據(jù)by now來判斷）
3)They must have been to the Great Wall,haven't they?
若是被動,應按被動結(jié)構(gòu)來處理.如：
1)The room must have been cleaned yesterday,wasn't it?
2)The room must have been cleaned,hasn't it?
若句中有表示過去完成時的時間狀語,問句部分應用hadn't.如:
They must have learnt 5000 English words by the end of last term,hadn't they?
(本題中must表推測,如果將它去掉,還原為真實句就是They had learnt 5000 English words by the end of last term.因此,反意問句是hadn't）