能告诉我分别用had+过去分词+should/would/could/might+have+过去...答:常用于主句中的形容词和过去分词有:advisable, appropriate, best, better, compulsory, crucial, desirable, fitting, imperative, important, obligatory, preferable, proper, decided, ordered, recommended, requested, required等。参考资料:情态动词及虚拟语气 – 个人日记 – 一百易社区 http://space...