问题
单项选择题
In the following statements about functional dependency, which one is incorrect ( )
A．if X’
X, then X→X'
B．if X→Y and Y’
Y, then X→Y'
C．if X→Y and X’
X, then X'→Y
D．if X→Y and Y→Z, then X→Z
答案
参考答案：C
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