People should have taken steps to stop this happening,but they___a.didn't b.haven't 选A B怎么排除的

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Peopleshouldhavetakenstepstostopthishappening,butthey___a.didn''tb.haven''t选AB怎么排除的Peopleshouldhavetak

People should have taken steps to stop this happening,but they___a.didn't b.haven't 选A B怎么排除的
People should have taken steps to stop this happening,but they___
a.didn't b.haven't
选A B怎么排除的

People should have taken steps to stop this happening,but they___a.didn't b.haven't 选A B怎么排除的
should have taken是虚拟语态,证明了这个stop this happening并没有发生,所以后面要用过去时.
haven't 首先不能和虚拟语态配合,其次,既然是虚拟语态了,所指的动作(take steps)一定是说话之前发生的,这就限定了时态,不可能是现在(完成)时.

此时的have是实义动词,实义的反义疑问要用did not.我用手机上的,不能很好的给你解释,不好意思!

人类本可以阻止这一切的发生,但是他们没有做到。

因为A听起来就比B来的好听,所以每当我遇到疑难选择题时几乎都是选择A,那么既然选择A了我当然就排除B了。谢谢`
飞飞

take是实义动词 而should只是代表虚拟语气必须要用的,而have是已经的have done形式的 又因为是过去完成时(虚拟的)用过去式 所以选A 而如果选B那have就是实义动词了
人们本可以采取一定的措施去阻止这一切的发生,可他们并没这么做!

Should people have cosmetic surgery? WE SHOULD RESPECT food and think aboutWe should respect food and think about the people who don’t have what we have here and treat food nicely意思 分析一个题目的句子结构We should respect food and think about the people who don’t have what we have here and treat food nicely People should have taken steps to stop this happening,but they___a.didn't b.haven't 选A B怎么排除的 People should have taken steps to stop this happening,but they___a.didn't b.haven't 选A B怎么排除的 i should don't have pushed it Most citizen think that the government -----the food standard,putting people's health atrisk . A can have lowered Bmustn't have lowered C should have lowered D shouldn't have lowered people should wash their hands ( )they have meals should people have surgery to make themselves more beautiful? 求文档: Young People Should Have Combatant Spirit 翻译:A teacher should have broad experience with young people If I would have listened to those people .27.If I would have listened to those people who told me I couldn’t do it then.,today ____ just be Saturday.A will B.shall C.would D.should 英语翻译句子的意思We should respect food and think about the people who don't have____we have here and treat food nicely . We should respect food and think about the people who don’t have_______ we have here and treat food nicely.A.that B.which C.what D.whether People should be good______wild animals.Don't scare them______. Some scientists t( ) that people should also take catnaps. should have done ,shouldn't have done.could have done,couldn't have done 1.Mr.White ______ at 8:30 for the meeting,but he didn’t’ show up.选项:a、should have arrived b、 should arrivec、 should have had arrived d、 should be arriving2.People around the world are becoming more and more ____ about the population e