"the tell tale story" how does the use of a first-person narrator contribute to the development of suspense

The use of first-person point of view contributes to the suspense because it constantly reminds the reader that he is a madman. And the more he tries to convince you he's not mad, the more you realize that he is. Not only that, but the words the narrator uses and the details the narrator gives also adds to the suspense. 

The answer is all of the above.