Which physical demand of combat requires lower body strength and stamina?

The correct choice focuses on the physical requirements associated with carrying wounded Marines to safety, which necessitates a significant amount of lower body strength and stamina. In combat situations, personnel may need to move quickly and efficiently while also managing the weight of another individual. This task can involve running or walking over uneven terrain, navigating obstacles, and maintaining the ability to respond to additional threats, all of which rely heavily on the strength of the legs and the cardiovascular endurance to sustain such physical exertion.

While other tasks listed, like climbing high obstacles or handling large-caliber ammunition, do require strength, they typically do not emphasize lower body strength and stamina to the same extent as the act of carrying a wounded comrade. Performing maintenance work is more about dexterity and technical skills rather than the physical demands of lower body strength. Thus, the act of rescuing and moving a wounded Marine encapsulates the quintessential need for both endurance and power in the lower body, making it the correct answer.