100 points
why did it take just six weeks for a keelboat to float down the mississippi to new orleans but four months to make the return trip?

a. keelboats carried a much heavier load on the return trip.
b. the return trip was upstream, against the flow of the river.
c. a keelboat's steam engine worked better with the wind than against it
d. once the goods had been delivered to new orleans, there was no hurry to get home.