How did the movement of cotton across America lead people to start traveling by train?

a. The boats that carried most of the cotton to market were too dangerous for passengers, once loaded down with cotton.

b. Trains were first use mainly to transport cotton; then railroads opened their tracks to other money-making opportunities.

c. Cotton sellers insisted on travelling along with their products, so railroad companies had to add passenger cars..

d. Cotton merchants never used trains as much as they used boats to transport cotton, so railroads looked for other ways to fill train cars.