What indicates a red weapon safety status for an M4 or M16?

The red weapon safety status for an M4 or M16 indicates that the weapon is ready to fire, which is characterized by specific conditions. When a magazine is inserted, there is a round in the chamber, the bolt is forward, and locked, this signifies that the weapon is in a state of readiness for immediate use.

This state is critical in military operations, as it allows a soldier to be prepared to engage a target swiftly, reflecting a heightened readiness during tactical situations. The other combinations do not represent a ready-to-fire condition; for example, having no magazine and an empty chamber or simply locking the magazine without ensuring a round is chambered indicates the weapon is not prepared for immediate action, which is not reflective of a red weapon safety status.

Thus, the specific conditions of having a magazine inserted, round in the chamber, and a locked bolt distinctly confirm that the weapon is set to fire, marking option B as the sole correct identification of a red weapon safety status.