Please be a little more specific but if you are asking what happened than pretty much Louis and Clark went west and found California, Oregon, Nevada ect.
The answer is A, because it is the most broad, and it is one of the main purposes that a government exists in the first place.
The colosseum was a building that could be flooded, and nowadays we use the same idea with swimming pools.
The idea being the colosseum was that people could come and see shows; we have stadiums and theatres for that today.
