高三英語Zoology
e.g. he must have gone to wuhan. （肯定已經去了）
he may / might / could have gone to wuhan. （可能已去了）
he can not / could not have gone to wuhan. （不可能已去了）
can he have gone to wuhan? （可能去了嗎？）
can(could)/may(might)/must/will等+have+done用來對過去發生的情況做出語氣強
弱不同的推測。具體使用時請注意以下幾點：
① can一般用于疑問句和否定句, 極少用于肯定句。
e.g. ---can she have gone to school?
---no, she can't have gone to school. i saw her just now.
② may表推測，一般不用于疑問句；疑問句中該用can, could或might。
e.g. how could he have forgotten such an important thing? （不用may）
might you have met him somewhere? （不用may）
③ could, may, might 用于肯定句語氣較弱，must用于肯定句語氣很強; may,
might 用于否定句語氣較弱，can, could 用于否定句語氣很強。
e.g. he could/may/might have gone to school. 他可能上學去了。
he must have gone to school. 他肯定是上學去了。
he may/might not have gone to school. 他也許沒去上學。
he can't/couldn't have gone to school. 他肯定沒去上學。
④ must表推測，一般不用于否定句；否定句中該用can或could。
誤：we mustn't have met before.
正：we can't have met before.
needn't + have + done 可用來表示“已做了多余的事”。
e.g. there is no school today. you needn't have come.
could + have + done 可用來表示沒做某事的“遺憾”。
e.g. she came here on foot, but she could have come by bus.
could / might + have + done 也可用來表示委婉的批評。
e.g. you could have come 5 minutes earlier.
you might at least have written me a letter.
在反意問句中，表推測的情態動詞不出現在簡短問句部分,取而代之的應是情態動
詞。句中有過去時間狀語的，問句部分用過去時，否則，用現在完成時。
e.g. he must have been there yesterday, wasn't he?
he must have been there, hasn't he?
he can't have been there yesterday, was he?
he can't have been there, has he?
三、由上我們可以得出一個結論：表推測時，must只用在肯定句中，而 can只用于否定句和疑問句中。而實際上can可用于肯定句中，但這常用于表可能性，意義有所不同，譯為“有時候可能”。
e.g. old newspaper can be useful.
舊報紙有時候還是有用的。
it can get quite cold here at night.
晚上這里有時候會相當冷。習題對話language pratice1. choose the proper word or phrase to take the place of the underlined word(s) in the sentences.①.glass=transparent ②. think=assume ③. make clear=clarity