Answer: B. King Duncan thinks Macbeth is good and virtuous man, when in reality Macbeth is plotting his murder.
Irony occurs when a character believes something that is the complete opposite of reality. For irony to work in a play, the audience usually has to have more information that the characters. In this case, the audience knows that Macbeth is planning the murder of King Duncan. However, the audience also knows that King Duncan believes Macbeth to be a good and virtuous man. This contradiction is an example of irony in the play.
The clause <em>when we can rest </em>is a subordinate/dependent clause, meaning that it cannot stand on its own - it has to be a part of a larger, independent clause, as is the case here.
