The correct option is A Dreary.
William's room felt dark, bleak, without any source of light or warmth. His dreadful days at work ended in his deary quarters. There is nothing treacherous about his surroundings, because, yes, it was predictable to him, just like anyone's own living quarters. He knows what waits him at home, making it more dreary. His monotony towards his quarters doesn't hint of being intolerable, for then, he wouldn't be there. Thus, the correct answer is option B.