Why did new towns spring up in places that were not near rivers or canals?

a. all of the land near rivers and canals was already occupied by the cities and towns.
b. the united states government sponsored new towns away from rivers and canals to attract settlers to the west.
c. the high levels of pollution in the country's rivers led people to settle areas that were far from those rivers.
d. the towns sprang up along newly laid railroad tracks. railroads could be built almost anywhere