Considering the time that has passed,the tired audience think the speaker must ____ most of the points he ought to ____.A.mention; cover B.have mentioned; coverC.mention; have covered D.have mentioned:have covered

Considering the time that has passed,the tired audience think the speaker must ____ most of the points he ought to ____.A.mention; cover B.have mentioned; coverC.mention; have covered D.have mentioned:have covered
Considering the time that has passed,the tired audience think the speaker must ____ most of the points he ought to ____.
A.mention; cover B.have mentioned; cover
C.mention; have covered D.have mentioned:have covered

Considering the time that has passed,the tired audience think the speaker must ____ most of the points he ought to ____.A.mention; cover B.have mentioned; coverC.mention; have covered D.have mentioned:have covered
B.have mentioned; cover
must have + 过去分词 用以对已发生的事作以肯定推测
ought to 要接动词原形.如接have+ 过去分词便带有“（过去）本应该.”（而事实上没有.） 带有责备意味,这与语境不符

D
“must+have+done”常用在肯定句中,表示对过去发生的行为的推测,意为"一定;想必"。例如:
Nonsense, you must have misheard.胡说，你肯定是听错了。（对过去的推测，很有把握的推测。）
His watch must have stopped. I will go and call him.他的手表肯定是停了。我去叫他。He mu...

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D
“must+have+done”常用在肯定句中,表示对过去发生的行为的推测,意为"一定;想必"。例如:
Nonsense, you must have misheard.胡说，你肯定是听错了。（对过去的推测，很有把握的推测。）
His watch must have stopped. I will go and call him.他的手表肯定是停了。我去叫他。He must have been looked down upon by his contemporaries.他一定是受到同龄人的轻视了。You must have seen the film Titanic.你一定看过电影《泰坦尼克号》。He must have been to Beijing. 他肯定去过北京。It must have rained last night, for the ground is wet. 昨天晚上一定下过雨了,因为地面是湿的。It is 8 o’clock. They must have arrived now. 8点了。现在他们一定已经到了。"ought to + 动词的完成式"表示过去应做某事而实际未做,其否定形式表示本不应该做某事却做了(同 should 用法),有责备或惋惜之意. 例如：You ought to have helped him, but you didn’t. 你本应该帮助他但你没有。（有责备之意）You ought to/ should have studied harder. 你本应该更努力学习的。（本该做，却没做，有责备之意）"ought to + 动词的完成式"用于否定句，表本不应该。He ought not to have stopped his work halfway.他本不应该做这项工作时半途而废。（有责备之意）He oughtn’t to/ shouldn’t have done that. 他本来就不该做那件事。（本不该做，却做了，有责备之意）

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C