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

Content of header file h1.h
------------------------------------------------
h1.h
#include <iostream>
using namespace std;
namespace A{
	int func(int a){
		cout<<"using namespace A";
		return 2*a;
	}
}
------------------------------------------------
 
Content of header file h2.h
------------------------------------------------
 
h2.h
#include <iostream>
using namespace std;
namespace B{
	float func(float a){
		cout<<"using namespace B";
		return 2*a;
	}
}
------------------------------------------------
 
Content of program.cpp
------------------------------------------------
 
#include <iostream>
#include <string>
#include "h1.h"
#include "h2.h"
using namespace std;
using namespace A;
using namespace B;
int main(int argc, char const *argv[])
{
	/* code */
	int a = 10;
	float b = 10.0;
	cout<<func(a)<<endl;
	cout<<func(b);
	return 0;
}
-----------------------------------------------

A. using namespace A10
using namespace B10

B. using namespace A20
using namespace B20

C. Error due to clash of func()

D. This is not allwed in C++

Answer: Option B