class A{public:void setA(int);private:int a;};class B{public:void setB(int);private:int b;};class C:public A, private B{public:void setC(int, int, int);private:int c;};void A::setA(int x){a = x;}void B::setB(int x){b = x;}void C::setC(int x, int y, int z){setA(x);setB(y);c = z;}int main(int argc, const char * argv[]) {C obj;obj.setA(5); // Aobj.setB(6); // Bobj.setC(6, 7, 9); // Creturn 0;}main函数中哪条语句是错误的

A
B
C