The option that did not make travel difficult in Texas prior to the railroad is c. Severe traffic congestion on the few roads that were available made it difficult to get from one city to the other. This is because during the time period before the railroad, there were only a few roads available in Texas, and they were often poorly constructed and muddy during wet weather, making travel by stagecoach difficult and dangerous. Additionally, some rivers in Texas were too shallow for ships to travel year-round, which also made travel by stagecoach necessary. Therefore, options a, b, and d all contributed to the difficulty of travel in Texas before the railroad.