多继承中的二义性问题

using namespace std;
class Base
{
public:
    Base(int i):b(i) {cout<<"Base constructor. b="<<i<<endl;}
    ~Base(){cout<<"Base destructor. b="<<b<<endl;}
    int GetB(){return b;}
private:
    int b;
};

class Base11:virtual public Base
{
public:
    Base11(int i,int j):Base(i),b11(j)
    {
        cout<<"Base11 constructor."<<endl;
    }
    ~Base11(){cout<<"Base11 destructor."<<endl;}
    void Print()
    {
        cout<<"Data in Base11. b11="<<b11<<",b="<<GetB()<<endl;
    }
private:
    int b11;
};
class Base12:virtual public Base
{
public:
        Base12 (int i,int j):Base(i),b12(j)
    {
        cout<<"Base12 constructor.";
    }
        ~Base12(){cout<<"Base12 destructor."<<endl;}
        void Print()
        {
            cout<<"Data in Base12. b12="<<b12<<",b="<<GetB()<<endl;
        }
private:
    int b12;
};
class Base2:public  Base
{
public :
    Base2(int i,int j):Base(i),b2(j)
    {
        cout<<"Base2 constructor."<<endl;
    }
    ~Base2() {cout<<"Base2 destructor."<<endl;}
    void Print()
    {
        cout<<"Data in Base2. b2="<<b2<<",b="<<GetB()<<endl;
    }
private:
    int b2;
};
class Derived:public Base11,public Base12,public Base2
{
public:
    Derived(int i,int j,int k,int l,int m,int n,int x,int y):Base11(i,j),Base12(k,l),Base2(m,n),Base(x),d(y)
    {
        cout<<"Derived constructor."<<endl;
    }
    ~Derived(){cout<<"Derived destructor."<<endl;}
    int GetD(){return d;}
private:
    int d;
};

int main()
{
    Derived obj(1,2,3,4,5,6,7,8);
    obj.Base11::Print();
    obj.Base12::Print();
    obj.Base2::Print();
    cout<<"Data in itself. d="<<obj.GetD()<<endl;
    return 0;
}

这个程序是我教材里的一个例子，但是我编译时报错，出现了二义性，想了一下，的却是的，而书本却能给出了下面的输出结果，想问是怎么回事？
Base constructor. b=7
Base11 constructor.
Base12 constructor.
Base constructor. b=5
Base2 constructor.
Derived constructor.
Data in Base11. b11=2,b=7
Data in Base12. b12=4,b=7
Data in Base2. b2=6,b=5
Data in itself. d=8
...