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7.10设某商业集团数据库中有一个关系模式R（商店编码，顾客编码，消费总额，顾客单位，地址，电话），该模式的关系记载每个顾客在每个商店的累计消费总额。如果规定：每个顾客在每个商店只有一个消费总额；每个顾客只属于一个单位；每个顾客单位只有一个地址、一个电话。请回答下列问题：（1）根据上述规定，写出模式R的基本函数依赖FD和候选码。（2）分析R是否为2NF。（3）分析R是否为3NF，如果不是，请将R分解成3NF。

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选出与这段文字的大概内容相近的选项Economic factors seem to explain less of why young adult women are increasingly likely to live at home. Generally, young women have had growing success in the paid labor market since 1960 and hence might increasingly be expected to be able to afford to live independently of their parents. For women, delayed marriage-which is related, in part, to labor market outcomes for men-may explain more of the increase in their living in the family home.

A. Young adults with a college degree found it easier to live independently of their parents.
B. Young men are less likely to end up as single parents than young women.
C. More young adult women live with their parents than before due to delayed marriage.
D. The percentage of young men who live with their parents has grown due to their decreased pay in recent decades.

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常用的液压执行元件主要包括液压缸和。

液压执行元件是将液体的转变成为机械能的装置。

液压缸的输入量是液体的和压力，输出量是和力。