The subject is often the doer of the action shown by the verb, and the object is often the thing or person to whom the action is done. One test that can help determine the subject is to add a tag question (like didn't she?, won't I?, will they?) - the pronoun in the tag (she, I, they) will stand for the subject in the sentence.
1. The man bought(cf - The man bought the CD, didn't he?)
2. The very suspicious but rather inexperienced spy used
3. The dog chased
In 3. there are actually two subjects and two objects – one in the main clause and one in the subordinate clause (a relative clause) that tells us about the cat, giving us:
that had recently broughtinto its owner's house.