虚拟语气              If从句                    主句

与现在事实相反       过去式                   would+动原

与过去事实相反     had+过去分词         should have+过去分词

suggest,recommend,insist,order,propose,require,request，commend,demand。动词形式：动词原形（ should+动词）

would rather+过去式

it is about time+过去式

as long as只要  as soon as一。。就。。  as far as多用在一些固定搭配中，与其连用的动词有：know,mean,said