单项选择题

若有以下程序: #include<iostream> using namespace.std; class data { public: int x; data(int x) { data::x=x; } ); class A { private: data d1; public: A(int x) :dl(X){} void dispa() { cout<<dl.X<<","; } }; class B:public A { private: data d2; public: B(int x) : A(x-1),d2(x){} void dispb() { cout<<d2.x<<endl; } }; class C:public B { public: C(int x) :B(x-1){} void disp() { dispa(); dispb(); } }; int main() { C obj(5); obj.disp(); return 0; } 程序执行后的输出结果是

A.5,5
B.4,5
C.3,4
D.4,3