I believe the answer is b.) flashbacks. Hope this helps!!!
It reveals the great depth of Macbeth's guilt, suggesting that all the water in the ocean cannot cleanse him of it.
Macbeth raises this question after he has killed Duncan. Therefore, he figuratively has "blood on his hands". This is a figure of speech that indicates someone is guilty of murder. Water often symbolizes purity or a cleansing. When people are baptized, they are covered in water to symbolize the washing away of sins. In Macbeth's question, he reveals that he may not be cleansed or forgiven for his sin of murder.
