下面给出的关系表r(A，B，C，D)满足下述哪个函数依赖______。
A．A
B．B
C．C
D．D
E．1
F．4
G．3
H．1
I．2
J．7
K．1
L．1
M．3
N．0
O．2
P．2
Q．1
R．2
S．3
T．3
参考答案：B
解析： 根据函数依赖的定义：关系R上不可能存在两个元组在X上的属性值相等，而在Y上的属性值不等，从表中看来只有B→D，所以本题的答案为B。
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