The best answer is industrial: it makes sense for people to settle in industrial regions, as they can hope to find work there. Other options refer to the distribution of people, such when people are from many cultures (multicultural) but this was not something people in 19th century searched for most, instead they wanted good job opportunities.
Silk Road:
The Silk Road specifically refers to the trading land routes that connects East and Southeast Asia to South Asia and Persia followed by Arabian Peninsula, East Africa and finally Southern Europe.
This network was regularly used from 130 BCE and part of that road is still in existence as a paved highway that connects Pakistan and the Uygur.
Chinese are the one who first started trading in this road and as its name indicates it is mainly used as a trade route for trading silks.
Hence this ancient road played a major role on times when it was constructed.
The correct answer is mountains. Erosion create mountains. It is an act of in which earth is worn away by water, ice and wind. It is the process of weathering, breaks down and dissolution of rocks that create such things. It also create hills and valleys.
