多重继承问题

[cityvagrant]

#include <iostream>
using namespace std;

class A
{
public:
static void printx()
{
cout << "A::printx" << endl;
}
};

class B
{
public:
static void printx()
{
cout << "B::printx" << endl;
}
};

class C: public A, public B
{
public:
static void printx()
{
cout << "C::printx" << endl;
}
};

void main(void)
{
//C.A::printx();
//C.B::printx();
//C::printx();

system("pause");
return;
}
为什么C.A::printx();不行啊