单项选择题

若有以下程序：
#include ＜iostream＞
using namespace std;
class Base

public:
Base ( )

x=0;

int x;
;
class Derivedl : virtual public Base

public:
Derivedl ()

x=10;

;
class Derived2 : virtual public Base

public:
Derived2 ()

x=20;

;
class Derived : public Derivedl,protected Derived2 ;
int main ( )

Derived obj;
cout＜＜obj .x＜＜end1;
return 0;

该程序运行后的输出结果是 ( )。

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