How do you salute on a challenging post when armed with the service rifle?

When saluting on a challenging post while armed with the service rifle, the correct method is to execute the Present Arms command. This action shows respect and adherence to the military customs and courtesies when you're equipped with your weapon.

The Present Arms position involves raising the rifle to a position of honor, allowing you to acknowledge the presence of a superior officer or to show respect in a formal manner. This is particularly important in a challenging post scenario, where you may be required to maintain readiness while also demonstrating proper military protocols.

The other options, such as a hand salute, Order Arms, or Right Shoulder Arms, do not encapsulate the formality and readiness required in this context. A hand salute, for instance, is used when unarmed or in certain more relaxed situations, while Order Arms involves returning the weapon to a non-ready position, which would not be suitable in a challenging post scenario. Right Shoulder Arms is a position for carrying the firearm but does not serve the purpose of saluting or acknowledging an officer.