Which of the following is the best example of situational irony?

a. in a bank-heist movie, it unexpectedly turns out that the robber is the banker's mother.
b. a book in which you know that a man is inside the protagonist's house waiting to kill him, but the protagonist is unaware of that as he enters the home.
c. a television show set in an emergency room of a hospital.
d. you tell your friend the dress she's wearing is "perfect for the occasion" even though you're going camping.