Perhaps the answer is when Macbeth kills the current king and is rewarded by being named king himself. Nobody expected he would turn bad and kill the king, he was formerly a good soldier, and that is why it is said that 'fair is foul' - he used to be good, but isn't anymore.
It's most likely A. because back then women were treated like common house hold objects; they were used and when they couldn't be used anymore thrown out.
Cite where you got the information from
The question that a reader should ask to identify an author's purpose is "Why did the author write this text?"
