Please help!

Dramatic irony is a literary device where the audience understands something that characters do not. Which statement best describes an effect of dramatic irony?

A.
It clarifies the climatic conflict in the story for the reader.
B.
It reveals a vital detail that the reader was previously unaware of.
C.
It creates a sense of suspense in the story for the reader.
D.
It creates a humorous mood in an otherwise serious event in the plot.