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}
集合{Ø, a, {a} }的幂集是:
A. { {Ø}, {a}, {{a}} }
B. { {a}, {{a}}, {a,{a}} }
C. {Ø, {a}, {{a}}, {Ø,a}, {Ø, {a}}, {a,{a}}, {Ø,a, {a}} }
D. {Ø, {Ø}, {a}, {{a}}, {Ø,a}, {Ø, {a}}, {a,{a}}, {Ø,a, {a}} }