The correct answer is - C.) The towns sprang up along newly laid railroad tracks. Railroads could be built almost everywhere.
Lot of new towns in the United States were established on places that were not close to springs or rivers. That was kind of breaking the unwritten rule, as the human settlements had always been developing next to a freshwater source.
The reason why this trend occurred where the newly laid railroad tracks. With the railroad tracks and the trains passing on them, the people were able to move quickly to other places, as well as trade very easily. The railroads replaced the river's usage for transportation and travel, so the towns didn't had problems developing in places like this since everything became very easily available.