虚拟语气：
1、中文：我要是你，我不会那么做。
（误）I shouldn't do that if I was you.
（正）I shouldn't do that if I were you.（表示与现在事实相反的虚拟语气不能用was，只能用were.）
2、中文：要是我父亲现在在这里，他会告诉我该做什么。
（误）If my father were here now，he will tell me what to do.
（正）If my father were here now，he would tell me what to do.（表示与现在事实相反的虚拟语气中，主句的助动词只能用would，might等过去时。）
3、中文：要是我知道她的电话号码，我就会给她打电话了。
（误）If I knew her telephone number，I would have called her.
（正）If I had known her telephone number，I would have called her.（表示与过去事实相反的虚拟语气中，条件从句的动词要用过去完成时。）
4、中文：要是昨天没下雨她也许会来。
（误）If it had not rained yesterday，he might come.
（正）If it had not rained yesterday，he might have come.（表示与过去事实相反的虚拟语气中，主句的动词要用助动词的过去时might，could等+HAVE+过去分词。）
5、中文：我不认为我会失败，但要是我失败了，我会再努力。
（误）I don't think that I shall fail. But if I failed，I would try again.
（正）I don't think that I shall fail. But if I should fail，I would try again.（表示与将来事实相反的虚拟语气中，条件从句的动词用should加原形动词。）
6、中文：他要是带了钱就会买它。
（误）Did he bring some money with him，he would have bought it.
（正）Had he brought some money with him，he would have bought it.（表示与过去事实相反的虚拟语气中，条件从句的动词要用过去完成时，若省略if，则用倒装形式。）
7、中文：她要是个男人可能会当选总统。
（误）Be she a man，she might be elected president.
（正）Were she a man，she might be elected president.（表示与现在事实相反的虚拟语气，不能用was，只能用were;若省略if，则将were放在句首。）
8、中文：我提议提高教师的薪资。
（误）I suggested that the teachers' wages could be increased.
（正）I suggested that the teachers' wages should be increased.（suggest当建议讲时，后面的名词从句的主要动词要用should加原形动词，should可以省略。）
9、中文：他这么做是重要的。
（误）It is important that he will do it.
（正）It is important that he do it.（It is important+that引导的名词从句的动词要用should加原形动词，should可以省略。）