Given the Following Class, Which Is the Correct Function Header

Given the following class, which is the correct function header for the display function?
Class Rational
{
Public:
Rational) ;
Rationalint numer, int denom) ;
Rationalint whole) ;
Int getNumerator) ;
Int getDenominator) ;
Friend void displayostream& out, const Rational& value) ;
Private:
Int numerator;
Int denominator;
};

A) friend void displayostream& out, const Rational& value)
B) void displayostream& out, const Rational& value)
C) void Rational::displayostream& out, const Rational& value)
D) friend void Rational::displayostream& out, const Rational& value)