Answer: A) by revealing an unhinged psychological state.
Explanation: Gothic fiction is a style of writing that is characterized by elements of fear, horror, death, suspense and gloom, as well as romantic elements, such as nature, individuality, and very high emotion. In the given excerpt from "The Adventure of the Mysterious Picture" we can see an example of Gothic fiction, because it conveys a sentiment of suspense and fear by revealing the unhinged psychological state of the speaker (he can not avoid looking at the picture).