![](https://lstatic.shangxueba.com/jiandati/h5/images/m_q_title.png)
有如下类声明:class XA{int x;public:XA(int n){x=n;}};class XB:public XA{int y;public:XB(int a, int b) ;};在构造函数XB的下列定义中,正确的是
A.XB::XB(int a,int B) :x(A) ,y(B) {}
B.XB::XB(int a,int B) :XA(A) ,y(B) {}
C.XB::XB(int a,int B) :x(A) ,XB(B) {}
D.XB::XB(int a,int B) :XA(A) ,XB(B) {}