单项选择题
In the following statements about functional dependency, which one is incorrect
A．If X→Y and Y→Z, then X→
B．If X→Y and Y'
Y, then X→Y'.
C．If X→Y and X'
X, then X'→
D．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'→D．If X'
X, then X→X'.