Explanation:

- The word "refractory" is often used to describe something or someone that is resistant to control or authority. It suggests a sense of defiance and difficulty in management.

- Option 1: Well-behaved means obedient, polite, and complying with rules. This is the opposite of refractory.

- Option 2: Stubborn means unyielding, determined, and resistant to change or control. It aligns closely with the definition of refractory.

- Option 3: Repay means to pay back or return something, and it’s unrelated to the concept of being refractory.

- Option 4: Peak refers to the highest point or greatest level, and doesn’t connect to the meaning of refractory.

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