Something must have happened on their way here,or they _____ by now.1.should have arrived 2.should arrive 3.would have arrived 4.would arrive 这道题的答案到底是1,3,4 那个,我看选1,3 的较多,还有选4的.

Something must have happened on their way here,or they _____ by now.1.should have arrived 2.should arrive 3.would have arrived 4.would arrive 这道题的答案到底是1,3,4 那个,我看选1,3 的较多,还有选4的.
Something must have happened on their way here,or they _____ by now.
1.should have arrived
2.should arrive
3.would have arrived
4.would arrive
这道题的答案到底是1,3,4 那个,我看选1,3 的较多,还有选4的.

Something must have happened on their way here,or they _____ by now.1.should have arrived 2.should arrive 3.would have arrived 4.would arrive 这道题的答案到底是1,3,4 那个,我看选1,3 的较多,还有选4的.
这道题是《2002年北京地区成人本科学士学位英语统一考试A卷试题》的第47题
47.Something must have happened on their way here.Or they _________by now.
　A.should have arrived　　B.should arrive　　C.would have arrived　　D.would arrive
答案：C虚拟语气.第一句是must+have +过去分词的结构,表示对过去事实的推测.The road is wet.It must have rained last night.路是湿的,昨晚上肯定下雨了.因此我们可以推断：这是一个和过去的事实相反的虚拟语气.should +have +过去分词的结构,表示对过去动作的责备、批评.如：You should have gone over your lessons.你应当把功课复习好的.但是此句只是一个表示和过去的事实相反的虚拟句子,并没有责备的意思.本句的意思是：“路上肯定出事了.否则,他们现在已经到了.”因此正确答案应该是C.

选1，by now 强调现在特定时间点，应该用完成时态
would have arrived 我理解是用于有条件前提下可以到达。
比如 if nothing happened on their way here, they would have arrived by now.
如果他们来的路上没发生什么事的话，他们是现在是可以到达的。
should have arr...

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选1，by now 强调现在特定时间点，应该用完成时态
would have arrived 我理解是用于有条件前提下可以到达。
比如 if nothing happened on their way here, they would have arrived by now.
如果他们来的路上没发生什么事的话，他们是现在是可以到达的。
should have arrived 是应该已经到达了。

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选1
should have done表示本应做某事，实际上却没做
该句译为：他们在路上一定遇上了什么事，不然他们现在应该到了。

must have happened 是对过去的猜测的虚拟语气，但后边有by now,所以本题是混合条件，即前边与过去相反， 后边与现在相反，排除1,3(与过去相反),我觉得选4,。2是应该来了， 与将来相反。

正确：1
by now 体现现在完成时。首先谢谢你，回答我的问题。
为什么不是选3呢？
我看别人在网上说的：[should have done 的意思一般理解为“本应该”，有“埋怨”的意思在里面，“本来该做的事情没有做”；而would have done 仅是表示与过去事实相反，并没有“应该”的意思，也没有埋怨该做的事情没做的含义。 ]。
其实，我在看成人学位外语的...

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正确：1
by now 体现现在完成时。

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