题目内容

下面N×N的笛卡尔积的子集中,哪些可以构成函数?

A. {(n1,n2) | n1,n2∈N and n1+n2 <10}
B. {(n1,n2) | n1,n2∈N and n2 = n1^2}
C. {(n1,n2) | n1,n2∈N and n1 = n2^2}
D. {(n1,n2) | n1,n2∈N and n2为小于n1的素数个数}

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