IF虛擬語氣的三種時態是：表示與事實相反的情況；表示與過去事實相反的情況；提出過去的未發生的條件
1、提出將來會發生的事：
主句：主語＋would/should/might/could＋動詞原形；
從句：should＋動詞原形/were to＋動詞原形；
例句：If he should go to Harvard University, he would make full use of his time.
2、提出現在的條件：
從句：動詞過去式；
例句：If he studied at this school, he would know the enviornment around the school very much.
3、提出過去的未發生的條件：
主句：主語＋would/should/might/could have＋動詞過去分詞；
從句：had＋動詞過去分詞
例句： If I had read the book, I would have told you about it.
IF虛擬語氣的三種時態是：表示與事實相反的情況；表示與過去事實相反的情況；提出過去的未發生的條件
1、提出將來會發生的事：
主句：主語＋would/should/might/could＋動詞原形；
從句：should＋動詞原形/were to＋動詞原形；
例句：If he should go to Harvard University, he would make full use of his time.
2、提出現在的條件：
主句：主語＋would/should/might/could＋動詞原形；
從句：動詞過去式；
例句：If he studied at this school, he would know the enviornment around the school very much.
3、提出過去的未發生的條件：
主句：主語＋would/should/might/could have＋動詞過去分詞；
從句：had＋動詞過去分詞
例句： If I had read the book, I would have told you about it.