Final answer:
The owner of an ox must pay if the ox is known to be a gorer, indicating responsibility for preventing harm from their animals.
Step-by-step explanation:
According to Article 251 of the Code of Hammurabi, the owner of an ox that gores a man must pay money if it is known that the ox is a gorer and the owner fails to take preventive measures such as binding the ox's horns or securing the animal.
Therefore, the correct answer is A: It is known that the ox is a gorer. The provided legal text suggests that there was an expectation of responsibility upon animal owners to prevent harm, especially if an animal had a history of dangerous behavior.