Final answer:
In the case of Jones being struck by a foul ball, the most likely legal defense would be 'assumption of risk,' owing to his awareness and acceptance of the risks associated with attending a baseball game.
Step-by-step explanation:
The concept most likely used in defense of the case where Jones, a baseball fan, is struck by a foul ball at a game would be c. Assumption of risk. This legal defense is often used in situations where the plaintiff voluntarily exposes themselves to a known hazard. In the context of watching a baseball game, spectators are generally aware that there is a possibility of being hit by a foul ball.
Courts have frequently recognized that fans assume this risk by choosing to attend the game, and therefore, the defense may argue that Jones assumed the risk of being struck. Unlike contributory negligence or comparative negligence, assumption of risk does not necessarily focus on the plaintiff's behavior in contributing to the accident but rather on their acceptance of the inherent risks involved in the activity.