The correct answer is B. The audience sees the killer behind the door, but the character is unaware until it is too late.
Step-by-step explanation:
Dramatic is a type of irony mainly used in narratives such as novels, stories or movies, in dramatic irony some information is provided to the audience or related to some situation or character, but this information is not known by other characters in the story, this implies dramatic irony increases the interests in the audience of readers by giving them clues on how a situation will be solved. In this case, as the audience is aware of the killer behind the other, but the character that is going to be killed does not know this there is dramatic irony as this information is ignored by the character being affected but know by the audience, which is what dramatic irony is about.