c++中的多态性，父类向量中的类型丢失

I have a class A, which is parent to classes B and C. And a class X, which is a parent to Y and Z.

class A {};
class B : public A {};
class C : public A {};


class X
{
    void foo(A) { std:: cout << "A"; }
};

class Y : public X
{
    void foo(B) {std::cout << "B"; }
};

class Z : public X
{
    void foo(c) {std<<cout <<"C"; }
};

int main()
{
    B b;
    C c;

    Y y;
    Z z;

    y.foo(b);//prints B // b is a B, and Y::foo takes a B, hence print B
    y.foo(c);//prints A // mismatch between types, fall back and print A
    z.foo(b);//prints A // mismatch between types, fall back and print A
    z.foo(c);//prints C // c is a C, and Y::foo takes a C, hence print C

    std::vector<A> v;
    v.push_back(b);
    v.push_back(c);

    //In this loop, it always prints A, but *this is what I want to change* 
    for (size_t i = 0; i < v.size(); ++i)
    {
        z.foo(v.at(i));
        y.foo(v.at(i));
    }
}

是否可以让项目打印与硬编码调用相同的结果?这意味着我会将它们视为原始类型，而不是其父类型?或者一旦我将它们放入 A 的向量中，它们将永远属于 A 类型?

vector<X*>