Be+动词过去分词 到底表状态?还是被动?还是可以理解成,动词的过去分词形式就变成了形容词? be动词的过去分词

“be动词加过去分词”和“过去分词”都表被动，怎么区别？ When asked to clean the room，he was unhappy.When(he was)asked to clean the room，he was unha...