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2014gre数学选择题精炼 Petworld has exactly fourteen animals that are kept in four separate cages according to the following conditions: Each cage contains exactly two, four, or six animals. Any cage containing a gerbil also contains at least one hamster; any cage containing a hamster also contains at least one gerbil. Any cage containing a lizard also contains at least one snake; any cage containing a snake also contains at least one lizard. Neither cage Y nor cage Z contains a gerbil. Neither cage W nor cage X contains a lizard. . Which one of the following could be a complete and accurate list of the animals kept in cages W and Y? W: one gerbil and one hamster; Y: two lizards and two snakes W: one gerbil and two hamsters; Y: one lizard and three snakes W: two gerbils and two hamsters; Y: one lizard and four snakes W: two gerbils and two hamsters; Y: three lizards and one snake W: two gerbils and two lizards; Y: two hamsters and two snakes . If there are exactly two hamsters in cage W and the number of gerbils in cage X is equal to the number of snakes in cage Y, then the number of snakes in cage Z must be exactly one two three four | 
