Step 1 — Understand the word:
The word restive means uneasy, impatient, restless, or difficult to control, especially when someone is unable to remain calm or still.
Step 2 — Interpret the nuance:
A restive person or situation suggests agitation, nervous energy, or a lack of calmness. It often applies to people who are hard to manage because of their impatience or agitation.
Step 3 — Find the antonym:
The opposite of being restless and agitated is being calm, peaceful, and undisturbed. The word placid means calm, tranquil, and not easily excited or agitated.
Step 4 — Fit in the context:
Thus, while restive conveys restlessness and unease, placid conveys calmness and composure, making it the most appropriate antonym.
Final Answer:
The correct option is (B) : Placid.