Final answer:
The correct identifier for defining the member function Display() outside the class is Option D. 'void Student::Display'. The scope resolution operator (::) connects the function name to its class.
Step-by-step explanation:
The correct identifier to use for the member function Display() definition in the given Student class is option d: void Student::Display. When defining a member function outside of the class declaration in C++, you should prepend the class name to the function name with the scope resolution operator ::. This signifies that the function Display is a member of the Student class. Hence the proper member function definition would look like this:
void Student::Display() {
// Function definition here
}
This syntax ensures that the Display function is associated with the Student class.