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.
a. Victoria Falls
Victoria Falls is a waterfall in southern Africa on the Zambezi River at the border of Zambia and Zimbabwe. It is one of the Seven Natural Wonders of the World. It is the largest waterfall in the world.
ANSWER: C
(Empire, kingdom, republic.)
All variations of their democracy.
