这种虚拟语气主要用在it is+形容词(名词,过去分词)+that+主语+should+动词原形(should可以省略)这种结构中。
常见的这类形容词有:advisable, anxious, better, desirable, surprising, natural, necessary, strange, important, regretful.
常见的这类过去分词有:decided, demanded, recommended, requested, desired, required, ordered, suggested.
常见的这类名词有:duty, pity, no surprise, no wonder, regret, shame.