Final answer:
Penicillin was the technology first used during World War II for treating battlefield infections; other options like airplanes, telegraphs, and machine guns were already in use before this conflict.
Step-by-step explanation:
The option that was used for the first time during World War II is penicillin. Airplanes, telegraphs, and machine guns were all utilized in warfare prior to World War II. Airplanes were used as early as World War I for reconnaissance, and later for combat roles.
The machine gun had already changed the nature of warfare dramatically by World War I, with the Maxim gun being a notable example from that era. Telegraphs had been in military use long before either of these conflicts. Penicillin, however, was used on the battlefield to treat infections in World War II for the first time, having been discovered in 1928 by Alexander Fleming and not mass-produced until the early 1940s.