What Is a Subplot? Thanks in advance

Select the correct answer. which of these lines from “the raven” by edgar allan poe to create the dark and gloomy tone of the poem? a. "'tis some visiter entreating entrance at my chamber door— some late visiter entreating entrance at my chamber door; b. once upon a midnight dreary, while i pondered weak and weary, over many a quaint and curious volume of forgotten lore— c. "and so faintly you came tapping, tapping at my chamber door, that i scarce was sure i heard you"—here i opened wide the door— d. bird or beast above the sculptured bust above his chamber door, with such name as "nevermore." hurry