Which of the following best describes a person characterized by "impassive" behaviors?

A person characterized by "impassive" behaviors is best described as calm and emotionally reserved. The term "impassive" refers to an individual who shows little to no emotional response, often appearing indifferent or unaffected by circumstances that typically elicit strong feelings. This demeanor suggests a certain level of composure and control over one’s emotions, which aligns perfectly with being calm and emotionally reserved.

The other options describe individuals who exhibit a range of emotional expressions and responses—such as being highly emotional and reactive, expressive and vivacious, or emotionally volatile and unpredictable—all of which contrast sharply with the idea of being impassive. Therefore, the best characterization of someone who is impassive is that they maintain a calm, composed, and reserved emotional state.