When asked to clean the room, he was unhappy.
When (he was) asked to clean the room, he was unhappy.
当从句中主语与主句中主语一致,而且从句中含有系动词时,可以省略从句中的主语和系动词.
如果过去分词做状语时也可以省略be
如: Cheated by the old man, the girl was very angry.
When asked to clean the room, he was unhappy.
When (he was) asked to clean the room, he was unhappy.
当从句中主语与主句中主语一致,而且从句中含有系动词时,可以省略从句中的主语和系动词.
如果过去分词做状语时也可以省略be
如: Cheated by the old man, the girl was very angry.