Which term describes a state that is calm and peaceful?

The term "placid" specifically refers to a state that is calm and peaceful. It conveys a sense of tranquility and serenity, often used to describe environments, conditions, or even individuals who exhibit a calm demeanor. When something is placid, it remains undisturbed or unruffled by disturbances or chaos, embodying a state of restful peace.

In contrast, the other options highlight states of turmoil or disturbance. For example, "chaotic" describes a situation characterized by disorder and confusion, often resulting in a lack of peace. "Upset" typically denotes feelings of distress or agitation, indicating anything but a calm state. Similarly, "agitated" refers to a state of anxiety or emotional disturbance. Thus, "placid" stands out as the only term that encapsulates a sense of calmness and peace.