Answer: C.
Explanation: In "The Masque of the Red Death," the gigantic clock of ebony most likely symbolizes C. the inevitability of death. The clock is described as "of the ebony, and the pendulum which swung to and fro was the representation of the constant and unheeded progress of time." The clock's black color, along with the ominous description of its pendulum's motion, suggests that it represents the passage of time toward death, which no one can escape. Its presence at the masked ball, where the revelers are trying to escape the deadly disease outside, emphasizes the theme of the inevitability of death and the futility of trying to avoid it.