¡¡¡¡5.In the United States£¬ vacationers account for more than half of all visitors to what are technically called ¡°pure aquariums¡± but for fewer than one quarter of all visitors to zoos£¬ which usually include a ¡°zoo aquarium¡± of relatively modest scope.
¡¡¡¡Which of the following£¬ if true£¬ most helps to account for the difference described above between visitors to zoos and visitors to pure aquariums£¿
¡¡¡¡£¨A£© In cities that have both a zoo and a pure aquarium£¬ local residents are twice as likely to visit the aquarium as they are to visit the zoo.
¡¡¡¡£¨B£© Virtually all large metropolitan areas have zoos£¬whereas only a few large metropolitan areas have pure aquariums.
¡¡¡¡£¨C£© Over the last ten years£¬newly constructed pure aquariums have outnumbered newly established zoos by a factor of two to one.
¡¡¡¡£¨D£© People who visit a zoo in a given year are two times more likely to visit a pure aquarium that year than are people who do not visit a zoo.
¡¡¡¡£¨E£© The zoo aquariums of zoos that are in the same city as a pure aquarium tent to be smaller than the aquariums of zoos that have no pure aquarium nearby.
¡¡¡¡6.In the United States£¬ the Postal Service has a monopoly on first-class mail£¬ but much of what is sent first class could be transmitted electronically. Electronic transmittal operators argue that if the Postal Service were to offer electronic transmission£¬ it would have an unfair advantage£¬ since its electronic transmission service could be subsidized from the profits of the monopoly.
¡¡¡¡Which of the following£¬ if each is true£¬ would allay the electronic transmittal operators' fears of unfair competition£¿
¡¡¡¡£¨A£© If the Postal Service were to offer electronic transmission£¬ it could not make a profit on first-class mail.
¡¡¡¡£¨B£© If the Postal Service were to offer electronic transmission£¬ it would have a monopoly on that kind of service.
¡¡¡¡£¨C£© Much of the material that is now sent by first-class mail could be delivered much faster by special package couriers£¬ but is not sent that way because of cost.
¡¡¡¡£¨D£© There is no economy of scale in electronic transmission¡ª¡ªthat is£¬the cost per transaction does not go down as more pieces of information are transmitted.
¡¡¡¡£¨E£© Electronic transmission will never be cost-effective for material not sent by first-class mail such as newspaper and bulk mail.
