World War I was the first modern war because of Group of answer choices tanks, machine guns, international organizations, total warfare, airplanes, u-boats, and poison gas nuclear weapons, machine guns, international organizations, total warfare, airplanes, u-boats, and poison gas tanks, machine guns, international organizations, drones, airplanes, u-boats, and poison gas tanks, machine guns, the UN, total warfare, airplanes, u-boats, and poison gas