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单项选择题

将一枚硬币重复投掷 n ‍次，以‍X 和 Y 分别表示正面向上和反面向上的次数，则 ‍X 和 Y 的协方差和相关系数分别为（）‍

A．-n/4，-1
B．-n/4,1
C．n/4，1
D．n/4，-1

判断题

By employing the method of“classifying by analogy”,the ancients established extensive connection between the five elements and the human body. The wood corresponds to the liver, the gallbladder, the eyes and the tendons. The fire corresponds to the heart, the large intestine, the tongue and the vessels.