In its size i had been greatly mistaken. the whole circuit of its walls did not exceed twenty-five yards. for some minutes this fact occasioned me a world of vain trouble; vain indeed! for what could be of less importance, under the terrible circumstances which environed me, than the mere dimensions of my dungeon? but my soul took a wild interest in trifles, and i busied myself in endeavors to account for the error i had committed in my measurement. the truth at length flashed upon me. in my first attempt at exploration i had counted fifty-two paces, up to the period when i fell;

which of the following words best describes the mood of the excerpt?
a. humorous
b. righteous
c. sinister
d. prosperous