<正>Betty:Black hens are cleverer than white ones, aren’t they?Larry:How do you know?Betty:Well, the black hens can lay white eggs, but the white hens can’t lay black eggs.贝蒂:黑母鸡比白母鸡聪明,对吗?拉里:你怎么知道?贝蒂:嗯,黑母鸡能下白蛋,可白母鸡不能下黑蛋。