if的虚拟语气用法 if的虚拟语气用法是怎样

1、提出将来会发生[文]的事：主句：主语＋[章]would/sho[来]uld/might[自]/could＋动词[搜]原形；从句：sho[猫]uld＋动词原形/[经]were to＋动词原形。例[验]句：If he should go to Harvard Universit[网]y, he would make full use of his time.如果他要[文]上哈佛大学的话，他[章]就会充分利用他的时[来]间了。 2、提出现在的条件[自]：主句：主语＋wo[搜]uld/shoul[猫]d/might/c[经]ould＋动词原形[验]；从句：动词过去式[网]。例句：If he studied at this school, he would know the enviornme[文]nt around the school very much.如果他在[章]这所学校学习的话，[来]他会很了解周边环境[自]。 3、提出过去的未发[搜]生的条件：主句：主[猫]语＋would/s[经]hould/mig[验]ht/could have＋动词过去[网]分词；从句：had[文]＋动词过去分词。例[章]句： If I had read the book, I would have told you about it.我如果看过本[来]书，我会把内容告诉[自]你了。