I'm not sure 100% what exactly this question is asking, but I know World War 1 was the first war to include Gas masks and Chemical warfare, so that is more than likely the answer.
it didnt apply to border staates but the answer to your test question is A to free all free all slaves.
Answer:
Yes, the plague was bad
Explanation:
Plagues can wipe out lots of people and/or make them sick. It can cause isolation and downfalls of entire empires.
