Which condition is NOT required for the M203 to be ready for firing?

The M203 grenade launcher requires specific conditions to be ready for firing to ensure both safety and operational readiness. For the weapon to be considered ready, it must typically be in a state where a round is chambered, the action or breech is closed, and the weapon is on safe.

Loading three rounds, as noted in option C, is not a requirement for the weapon to be prepared for use. The M203 can operate with just one round in the chamber while being on safe. The emphasis on having a single round loaded ensures that the weapon is ready for immediate engagement without unnecessary complexity or risk associated with a fully loaded magazine.

The other options present scenarios that align with safety protocols, underlining the importance of the weapon being in a safe state with an appropriate round configuration. Thus, the requirement for three rounds is not applicable for making the M203 ready to fire, making it the correct answer to the question.