求if的虚拟语气用法,需要怎样注意时态的问题,

should(第一人称)和would(第二三人称)+动词原形
should(第一人称)和would(第二三人称)+have+过去分词
If I were you,I should take his advice.
He said he would go if I went.
If father hadn't sent me,I shouldn't have come.
另:
had+过去分词,用于一切人称和数
If we had left earlier,we wouldn't have missed the train.
(美国英语的结果主句,不管什么人称,都常用would)
以上should,would均为情态助动词.即本身无实意,只是构成时态语态作用.
以下为情态动词用于虚拟语气的情况
It might help a little if only you would keep clean.
只要你愿意保持清洁,可能就会好一点.
If you left at ten,you should arrive in time.
如果你十点动身,你就会及时到达.(should在这里意味着可能,有的句子中还表示应该)
I couldn't be angry with him if I tried.
我即使想生他的气,也做不到.(could有不能的意思)
特殊:
情态动词May(might)是一种特殊的虚拟语气,可用在句中表目的,让步.
He died in order that others might be saved.
他为了拯救别人而死.
这些是虚拟时态涉及你说的这四个词的部分.还有很多其他的问题.重要的是多做练习,多记范例.

If it had happend earlier ,there would be many more deaths.