if用于虚拟语气,主句用would,could,should,might+动词原形,这4个词可以互换吗?请区别性的造句

if用于虚拟语气,主句用would,could,should,might+动词原形,这4个词可以互换吗?请区别性的造句 if用于虚拟语气,主句用would,could,sould,might+动词原形,这4个词可以互换吗?如果不可以,请说明他们的区别,并举例 关于虚拟语气中should用法的问题,那天我查看if引导的虚拟语气的语法内容.说在主句中的should只用于第一人称,would可以用于各种人称.可是例句中又有if he should come,i would tell him.he 是第二人称啊 would appreciate it if句型必须用虚拟语气吗? what if用于虚拟语气吗? 虚拟语气中对过去的虚拟主句否定是用would have not done or would not have done? 虚拟语气,主句一般现在时,从句用现在时还是过去时?If you leave now,you would never regret it.还是you will never regret it.对呢？ 请问这句话是虚拟语气吗?he would have paid twice much as for the house if the salesgirl had insisted because he really wanted it那天我查看if引导的虚拟语气的语法内容。说在主句中的should只用于第一人称，would可 如何判断这句话要填入虚拟语气呢?另外如何判断虚拟语气添什么.Shall I stay here? I'd rather____ with us[A] you came[B] you would come是不是只有if引导的虚拟语气,主句才用 if.,主语＋would（等）＋动词 if 从句用过去时,主句用什么时态?（真实条件句,不是虚拟语气） i would be glad if you could help me.是不是虚拟语气,对过去i would be glad if you could help me.是不是虚拟语气,对过去情况的虚拟,条件句用过去完成时,主句用would/should/might/could+have+过去分词.我实在不会, 英语虚拟语气 200分在if引导的虚拟语气中,主句用would have done（与过去相反）或would do（现在相反）,从句用had done或did,were和were to do.但在as if ,if only ,but for等词引导的虚拟句中,却只能用上面的 if only虚拟语气if only引导的是虚拟条件句还是主句? she looked at me as if I were a stranger. 老师说这里用虚拟语气,可是怎么知道这是虚拟语气呢?我知道与现在事实相反可以用虚拟语气：从句谓语动词用过去式,主句用 would+动词原型；可是这里没有wou If they had studied hard, they could do it easily now 这个虚拟语气中这个虚拟语气中,虚拟语气是与过去事实相反,从句用had+过去分词,那么主句不是应该用should/would/could/might+have过去分词的吗? 为什么这 if 从句小疑问if 引导状语从句,主句用将来时,从句用一般现在时.比如:She will tell you the truth if she comes back tomorrow.但是如果是if 表示虚拟语气时,比如对现在的虚拟,主句就用would do,从句用过去式 I would be much grateful if you could help me seek out a girl第一问：为什么从句用could 主句用would be 第二问：是表与过去将来事实相反的虚拟语气吗 what would you do if you saw the traffic accident ,不是主将从现么if引导的条件状语从句虚拟语气的时候,主句什么时态