(NOT CLEAR)  Question 14: What is the correct declaration for a file stream insertion operator for a class my_stuff::my_class a

#include <fstream>

namespace my_stuff
{
class my_class
{
public:
int i;
};

//Declaration goes here

}//ns my_stuff

A. std::ofstream& operator<<(std::ofstream& ofs, const my_class&);
B. const my_class& operator<<(const my_class&)
C. std::fstream& operator<<(std::fstream& fs, const my_class&)
D. std::ifstream& operator<<(std::ifstream& ifs, const my_class&)
E. void operator<<(const my_class&)