[单选题]

Let R and S be the relation respection respectively：
Relation R:A B C Relation S:B C D
1 2 3 2 3 4
6 7 8 2 3 5
9 7 8 7 8 1
The number of tuples that the result of the expression R∞S(Here if natural join of relations R and S) is (69) ．(69)
A．1
B．4
C．7
D．10

Let R and S be the relation respection respectively：Relation R:A B C Relation S:B C D1 2 3 2 3 46 7 8 2 3 59 7 8 7 8 1The number of tuples that the result of the expression R∞S(Here if natural join of relations R and S) is (69) ．(69) A．1B．4C．7D．10