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阅读理解DPreparing Cities for Robot Cars The possibility of self-driving robot cars has often seemed like a futurist's dream, years away from materializing in the real world. Well, the future is apparently now. The California Department of Motor Vehicles began giving permits in April for companies to test truly self-driving cars on public roads. The state also cleared the way for companies to sell or rent out self-driving cars, and for companies to operate driverless taxi services. California, it should be noted, isn't leading the way here. Companies have been testing their vehicles in cit采用下列哪组方法，可以依次解决①～④中的遗传问题①鉴定一只白羊是否是纯种          ②在一对相对性状中区分显、隐性③不断提高小麦抗病(显性性状)品种的纯合度  ④检验杂种F1的基因组合A.杂交、自交、测交、测交B.杂交、杂交、杂交、测交C.测交、测交、杂交、自交D.测交、杂交、自交、测交