有如下程序:
#include<iostream>
using namespace std;
class Part
public:
Part(int x=0):val(x) cout<<val;
~Part()cout<<val;
private:
int val;
;
class Whole
public:
Whole(int x ,int y, int z=0):p2(x),p1(y),val(z)cout<<val;
~Whole()cout<<val;
private:
Part p1,p2;
int val;
;
int main()
Whole obj(1,2,3);
return 0;
程序的输出结果是( )。
A.123321
B.213312
C.213
D.123123