Given the set a = {2, 3, 4}, B = {2, 4, 6, 8}, C = {(x, y) | x ∈ a, y ∈ B, and logxy ∈ n *}, then the number of elements in C is () A. 9B. 8C. 3D. 4
When ∵ logxy ∈ n *, ∵ x = 2, y = 2, or 4, or 8; when x = 4, y = 4. ∵ C has four points (2,2), (2,4), (2,8), (4,4). That is to say, the number of elements in C is 4
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