The answer is C and E, hope this helps. :)
There are two reasons one was to follow after Pancho Villa and 2nd was to start a revolt (someone already asked this question XD)
To design and implement a better sewage drainage system for the city
The description best fits the kingdoms of Ghana and Songhai is the trading states of West Africa. Back then, the kingdom of Ghana and Songhai was really famous around the world for their Gold Resources. A lot of European merchants came to these kingdom to do a trade