Which of the following is a fundamental rule of firearm safety?

Assuming every firearm is loaded is a fundamental rule of firearm safety because it fosters a mindset of caution and responsibility. This principle ensures that regardless of your knowledge or experience with a particular firearm, you consistently treat it as though it can discharge a round at any moment. This approach minimizes the risk of accidents, as it compels individuals to handle firearms with the utmost care and respect at all times, whether they believe a firearm is loaded or not.

In a safe handling environment, this rule contributes significantly to preventing negligent discharges. It encourages shooters to follow other safety precautions, such as keeping the firearm pointed in a safe direction and keeping their finger off the trigger until ready to shoot.

The other options do not align with the core principles of firearm safety. Pointing the firearm at a friend violates the safety rule regarding where a firearm should be aimed. Storing firearms in an unlocked case does not provide adequate security and can lead to unauthorized access, especially by children. Lastly, cleaning firearms after every use is not necessarily a fundamental safety rule, although proper maintenance is important; it does not encompass the immediate safety practices required while actually handling a firearm.