Question: Consider a class named `CustomData`. Which choice is a correct declaration syntax to overload the postfix `++` operator as a class member?

1. `CustomData& operator++();`
2. `void operator++(CustomData);`
3. `CustomData operator++(CustomData);`
4. `CustomData operator++(int);`

Answer: The correct answer of the above question is Option D:`CustomData operator++(int);`