loudspeakerswerefixedinthehallsothateveryoneanopportunitytohearloudspeakerswerefixedinthehallsothateveryoneanopportunitytohearthespeach.AoughttoBmusthaveCmayhaveDshouldhave为什么选D不选A?这是虚拟语气

Question

loudspeakers were fixed in the hall so that everyone an opportunity to hear
loudspeakers were fixed in the hall so that everyone an opportunity to hear
the speach.
A ought to B must have
C may have D should have
为什么选D不选A?
这是虚拟语气吗？我怎么觉得不是？

Answer 1

虚拟语气不仅用于条件从句,下面的从句也需要用虚拟语气：
1.表示个人意愿（如建议、命令、要求、主张等）的名词从句——动词要用 should do 或者省略 should 直接用动词原形 do,如：
1）宾语从句：I suggested that he (should) leave for the city tomorrow.
2）主语从句：
it is essential that he (should) do it right away.他有必要马上就做这件事.
It is important that we (should) consider such a matter before everything.优先考虑这种问题是紧要的.
It is suggested that he (should) leave for the city tomorrow.
2）so that / in order that 引导的的目的状语从句,谓语动词必须含有can/could、may/might、should 等情态动词.如本题：
loudspeakers were fixed in the hall so that everyone should have an opportunity to hear
the speach.
选项都是情态动词但是意思各不相同——
A ought to ：用于表示义务或责任上的应该,用在本题不合题意.
B must have：表示道德良心、法律或者习惯所要求的应该,不合题意.
C may have：原题主句用的是过去时态,只有 might have 方可以在此处表示有可能的意思,因此是时态错误.
D should have 表示期望到的可能性,用在本句中意思是“大厅里都安装过扩音器,以便期望大家都有机会听到讲演”.