Answer:
The correct answer is D. Sinking.
Step-by-step explanation:
The attitude of the speaker or author towards the text is what we call the tone. When a text has elements like fear, horror, death, gloom and sometimes romantic elements, we can say that the tone of that text is gothic. And in the given passage from "The Fall of the House of Usher" by Edgar Allan Poe, the word "sinking" contributes to the gothic tone.