Which of the following is NOT a rule for legally displaying a firearm?

The correct choice points out that displaying a firearm with ammunition is not a rule for legal display. Legal display of firearms generally involves ensuring they are rendered safe and secure. This is crucial for maintaining safety and preventing accidental discharges or unauthorized access.

When firearms are displayed unloaded, it minimizes the risk of accidental discharge. Additionally, rendering a firearm inoperable, such as using a lock or removing critical components, ensures that it cannot be fired. Safe storage and displaying practices also require that firearms be in locations not easily accessible to unauthorized individuals, particularly children. Thus, displaying a firearm with ammunition contradicts these safety principles, as it presents an unnecessary risk.