单项选择题
Under the following inheritance hierarchy, which constructor is incorrectly implemented ( )
class A{
protected: int a;
public : A( int );
};
class B : public A
{ int b;
public:
B(int x, int y);
} ;
class C: protected B{
char c;
public:
C(char c, int x, int y);
} ;
A、A::A(int a):a(a){ }
B、B::B(int x, int y): A(x), b(y){ }
C、C(char cc, int x, int y): B(x, y),c(cc){ }
D、 C(char cc, int x, int y): A(x), B(x, y),c(cc){ }