Which of these were used in World War II but NOT in World War I?

A) poison gas

B) machine gun fire

C) aircraft carriers

D) use of automobiles

World War I did have machine guns, so you can rule that one out.

Mustard Gas was used, so you can rule that out for poison.

Automobiles were used, so you can rule that out.

Aircrafts were just new in 1917 at the end of the first world war. They couldn't carry anything but a pilot.

So I would say Aircraft Carriers.

Air carriers were not invented during World war I