TOEFL Listening: TPO-TOEFL阅读TPO - 304NTJMZ02QU8W5NN$

Which of the following can be inferred from paragraph 5 about flatboats and keelboats? A. They ceased to be used as soon as the first turnpikes were built. B. They were slower and more expensive to operate than steamboats. C. They were used for long-distance but not for regional transportation. D. They were used primarily on the Erie Canal.