A Sergeant Major in the Marines is equivalent to what rank in the Air Force?

The correct answer is Chief Master Sergeant. In the United States military, there are different rank structures across branches, but equivalent ranks can be drawn from their roles and responsibilities. A Sergeant Major in the Marine Corps is generally the highest enlisted rank, focusing on advising and assisting with the enlisted force's readiness and welfare.

In the Air Force, the Chief Master Sergeant holds a position of similar seniority and responsibility. This rank is also the highest enlisted grade in the Air Force and involves a significant role in leadership and management, much like that of a Sergeant Major in the Marine Corps.

Other options, while they represent senior enlisted ranks in the Air Force, do not match the level of responsibility and authority of a Sergeant Major. For instance, a Master Sergeant and a Senior Master Sergeant hold lower ranks compared to a Chief Master Sergeant, and a First Sergeant is a specific duty position that does not have a direct equivalent in terms of rank when it comes to comparing it with the overall duties of a Sergeant Major. Hence, Chief Master Sergeant is the most appropriate equivalent rank in the Air Force for a Sergeant Major in the Marine Corps.