Answer:
Because it shows only what the narrator knows at any given point, it increases suspense and tension.
Step-by-step explanation:
The first-person point of view is used to relate the reader with the narrator, in the sense that the audience can get to know the narrator's emotions, thoughts and drives. As a result, in "The Pit and the Pendulum," the author Edgar Allan Poe creates a feeling of suspense and terror as the narrator describes in detail the physical and mental tortures he is experiencing.