Which of the Following Would Be an Appropriate Function Declaration

Multiple Choice

Which of the following would be an appropriate function declaration to add two rational numbers?

A) void friend operator+ const Rational &left, const Rational &right) ;
B) void operatator+ const Rational &left, const Rational &right) ;
C) friend Rational operator+ const Rational &left, const Rational &right) ;
D) Rational operator+ const Rational &left, const Rational &right) ;