Which of the following best characterizes a "sullen" demeanor?

The term "sullen" is often used to describe an individual who is gloomy, moody, or withdrawn, displaying an air of sadness or sulkiness. Therefore, a sullen demeanor is characterized by feelings of discontent or disappointment that can result in a sulky attitude. This aligns closely with the choice that represents someone who is "sad and sulky."

In contrast, the other descriptors do not match the essence of being sullen. A cheerful and jovial demeanor conveys positivity and happiness, which is the opposite of sullen. Similarly, an excited and enthusiastic demeanor suggests energy and eagerness, again contrasting sharply with the dullness usually associated with sullen behavior. Finally, a calm and content demeanor implies peace and satisfaction, which lacks the dark, brooding quality inherent in someone who is sullen. Thus, the best characterization of a "sullen" demeanor is indeed the one that conveys feelings of sadness and sulkiness.