How should a soldier respond when an officer enters the room while inside and not in formation?

When an officer enters a room, the appropriate response is to call the room to attention. This action demonstrates respect and acknowledges the presence of the officer, adhering to military customs and courtesies. Calling the room to attention signifies that all personnel should become alert and respectful in the presence of a higher-ranking individual.

This practice is a vital part of military discipline, underscoring the hierarchical structure and the importance of etiquette within the military environment. The other choices do not reinforce the necessary level of respect required in such situations. For example, standing at ease or remaining seated does not appropriately recognize the officer’s presence, and while greeting verbally shows respect, it does not follow the full formal protocol of calling the room to attention.