感觉这道题B，C都对啊，答案是B，请牛人讲解一下吧～～～谢谢
29.The price of a full-fare coach ticket from Toronto to Dallas on Breezeway Airlines is the same today as it was a year ago, if inflation is taken into account by calculating prices in constant dollars. However, today 90 percent of the Toronto-to-Dallas coach tickets that Breezeway sells are discount tickets and only 10 percent are full-fare tickets, whereas a year ago half were discount tickets and half were full-fare tickets. Therefore, on average, people pay less today in constant dollars for a Breezeway Toronto-to-Dallas coach ticket than they did a year ago.
Which one of the following, if assumed, would allow the conclusion above to be properly drawn?
(A) A Toronto-to-Dallas full-fare coach ticket on Breezeway Airlines provides ticket-holders with a lower level of service today than such a ticket provided a year ago.
(B) A Toronto-to-Dallas discount coach ticket on Breezeway Airlines costs about the same in constant dollars as they did a year ago.
(C) All full-fare coach tickets on Breezeway Airlines cost the same in constant dollars as they did a year ago.
(D) The average number of coach passengers per flight that Breezeway Airlines carries from Toronto to Dallas today is higher than the average number per flight a year ago.
(E) The criteria that Breezeway Airlines uses for permitting passengers to buy discount coach tickets on the Toronto-to-Dallas route are different today than they were a year ago.
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