The correct answer is B. It creates a sense of suspense in the story for the reader.
Step-by-step explanation:
As mention in the question, dramatic irony focuses on providing key information to the reader that is not known by some characters. For example, the reader might know one of the characters is conspiring against the main character or hero but this character completely ignores this information. One of the main effects this has is a sense of suspense or tension because the reader expects the involved character to finally discover the truth. For example, the reader waits for the character to finally discover the conspiration and act against it. Thus, one effect of dramatic irony is "It creates a sense of suspense in the story for the reader".