20. Why does the author mention the first Baedeker Travel Guide to the United States? (A) To explain where tourists could find train and trolley schedules (B) To identify a way used by George Pullman to attract tourists to Pullman (C) To indicate how a large number of foreign tourists became interested in visiting the town of Pullman (D) To provide evidence that tourists were often more interested in visiting Pullman than in seeing the World's Columbian Exposition