Classes

Given the following class, what is syntactically wrong with the implementation of the display function?
class Rational
{
public:
Rational( );
Rational(int numer, int denom);
Rational(int whole);

int getNumerator( );
int getDenominator( );

friend void display(ostream& out, const Rational& value);
private:
int numerator;
int denominator;
};

void display(ostream& out, const Rational& value)
{
out << value.getNumerator( ) << '/"<< value.getDenominator( );
}
Choose one answer.

a. out should be pass by value.

b. nothing

c. value must not be pass by reference.

d. The get functions are not const functions.