若有以下程序：
#include ＜iostream＞
using namespaces std;
class A

public:
A()
A(int i)

x1=i;

void dispa()

cout＜＜’x1="＜＜x1＜＜",";

private:
int x1;
;
class B: public A

public:
B()
B(int i):A(i+10)

x2=i;

void dispb()

dispa();
cout＜＜"x2="＜＜x2＜＜end1;

private:
int x2;
;
int main()

B b(2);
b.dispb():
return 0;

程序运行后的输出结果是

A．x1=10,x2=2

B．x1=12,x2=10

C．x1=12,x2=2

D．x1:2,x2=2