What command indicates that the section may fire previously loaded rounds?

The command that indicates that the section may fire previously loaded rounds is "Cease loading." This command signals that no additional ammunition should be loaded into the weapon system, meaning that the crew can focus on firing the rounds already in the chamber or ready to be fired. When this command is given, it implies readiness to engage and execute the firing plan without any load adjustment.

In contrast, the other commands have specific meanings in the context of artillery operations. "Fire for effect" instructs the section to fire a predetermined number of rounds with the intent to accomplish a specific tactical goal, but does not indicate anything about previously loaded rounds specifically. "Adjust fire" is a command used for making adjustments to the trajectory of rounds based on observed impacts, typically requiring additional calculations or coordination. "Prepare to fire" indicates readiness to fire, but it does not imply a directive to stop loading ammunition, as the section may still be in the process of loading additional rounds.

Thus, "Cease loading" is the best indicator that the section can proceed to fire the rounds that have already been prepared.