Which action involves physically harming another without the use of a weapon?

The correct action that involves physically harming another without the use of a weapon is assault. This term covers a range of behaviors and can include acts such as hitting, pushing, or any other form of physical aggression that does not necessarily involve a weapon. Assault is considered a criminal offense and is defined by the intent to cause injury or the act of causing harm to another person.

In contrast, discharging firearms inherently involves the use of a weapon, thus removing it from consideration regarding actions that do not involve weaponry. Illegal parking pertains to a traffic violation and does not involve any physical harm to a person, while driving under the influence, while dangerous, primarily relates to impaired operation of a vehicle rather than direct physical harm to another individual. Therefore, the specific nature of assault fits the criteria of causing physical harm without a weapon, making it the correct choice.