Which statement is false?

a. Based on whether an operator is implemented as a member function or as a non-member function, the operator is used differently in expressions.
b. When an operator function is implemented as a member function, the leftmost (or only) operand must be an object (or a reference to an object) of the operator's class.
c. Operator member functions of a specific class are called (implicitly by the compiler) only when the left operand of a binary operator is specifically an object of that class, or when the single operand of a unary operator is an object of that class.
d. Another reason why you might choose a non-member function to overload an operator is to enable the operator to be commutative.

a. Based on whether an operator is implemented as a member function or as a non-member function, the operator is used differently in expressions.