Final answer:
The answer to the question is option 3) Pre-existing public duty. This principle states that someone with a public duty to perform an action is not entitled to a reward for fulfilling that duty. Therefore, as a fireman, Mike is not entitled to the reward for rescuing the cat.
Step-by-step explanation:
The student's question involves a legal concept related to contractual obligations and public duty. The correct answer is option 3) Pre-existing public duty. This legal principle states that if someone has a public duty to perform a certain action, such as a fireman's duty to rescue individuals or pets in distress, they are not entitled to collect a reward for performing that duty. In this scenario, Fireman Mike already has the public duty to rescue the cat regardless of any reward, so Karol is legally correct in asserting that she does not have to pay the reward to Fireman Mike.