1.动词suggest，order，demand，propose，request，command，insist等后的宾语从句中，用虚拟语气（即Should+动词原形或只用动词原形）来表示愿望、建议、命令、请求等。在动词wish /would rather后的宾语从句中，用过去式表示与现在事实不符，用过去完成式表示与过去事实不符。e.g. I suggest that we（should）set off at once． The doctor insisted that the patient (should)be X-rayed． I wishI were as strong as you． I would rather that you hadn't told him．2. 在 suggestion， proposal，idea，plan，order，advice等名词后的表语从句、同位语从句中要用虚拟语气，即should+动词原形或只用动词原形。如： Our suggestion is that you（ should）be the first to go． My advice is that we（should）send for Doctor Li． Do you know the order that you（should）keep watch？3. 在It is necessary/important/strange/natural；It is requested/suggested/desired/proposed；it is a pity等结构后的主语从句中要用虚拟语气，即Should+动词原形或只用动词原形。如： It is necessary that he（should）be sent there at once．It is requested that Professor Li（should）give us a speech．It is desired that we（should）get everything ready by tonight
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