An（ ），serving a function similar to a physical wallet,holds credit card numbers,electronic cash,owner identification,and owner contact information and provides that information at an electronic commerce site"s checkout counter.

单选题

An（ ），serving a function similar to a physical wallet,holds credit card numbers,electronic cash,owner identification,and owner contact information and provides that information at an electronic commerce sites checkout counter.

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判断题

flatMap(func)方法与map(func)方法相似，因此可以任意使用。-----------【判断题】

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