What is the characteristic of someone who is described as "querulous"?

Describing someone as "querulous" means that they tend to be peevish and complain a lot. This term captures a sense of discontent and irritability, often characterized by a tendency to express grievances or dissatisfaction. Therefore, the characteristic of being quick to complain or prone to whining aligns perfectly with the meaning of "querulous." In contrast, the other options describe states of being that are quite the opposite—whether it's being content, joyful, or calm—none of which fit the definition of someone who is querulous. Thus, identifying the correct characteristic underscores the essence of the word and its implications in describing personality traits.