单选题 有如下程序：
#include＜iostream＞
using namespace std;
class Basel{
public:
Basel(int d) {cout＜＜d;}
～Base1(){}
};
class Base2{
public:
Base2(int d) {cout＜＜d;}
～Base2(){}
};
class Derived:public Base1,Base2{
public:
Derived(int a,int b,int c,int d);
Base1(b),Base2(a),b1(d),b2(c) {}
Private:
int b1;
int b2;
};
int main(){
Derived d(1,2,3,4);
return 0;
}
运行时的输出结果是______。