What will be the output of the following C++ code?

#include <iostream>
using namespace std;
class sample
{
    public:
    sample() 
    {  
        cout << "X::X()" << endl; 
    }
    sample( sample const & ) 
    {  
        cout << "X::X( X const & )" << endl;
    }
    sample& operator=( sample const & )
    { 
        cout << "X::operator=(X const &)" << endl;
    }
};
sample f() 
{
    sample tmp;
    return tmp;
}
int main() 
{
    sample x = f();
    return 0;
}

A. X::operator=(X const &)

B. X::X( X const & )

C. X::X()

D. X::operator

Answer: Option C