Reference variables and const class members _____

The correct answer is: C. must be initialized, rather than assigned values.

A reference variable is a variable that stores the address of another variable. A const class member is a member of a class that cannot be modified after it has been created.

When a reference variable is initialized, the address of the variable that it is referencing is stored in the reference variable. When a const class member is initialized, the value of the member is stored in the member.

In C++, reference variables and const class members must be initialized, rather than assigned values. This is because reference variables and const class members cannot be reassigned. If a reference variable or const class member is assigned a value, the compiler will generate an error.

Here is an example of how to initialize a reference variable:

c++
int x = 10;
int& y = x; // y is a reference to x

In this example, the reference variable y is initialized to the address of the variable x. The value of x cannot be changed, but the value of y can be changed. For example, the following code will change the value of y, but it will not change the value of x:

c++
y = 20;

Here is an example of how to initialize a const class member:

c++
class C {
public:
const int x = 10;
};

In this example, the const class member x is initialized to the value 10. The value of x cannot be changed, even if the object of type C is modified. For example, the following code will not compile:

c++
C c;
c.x = 20; // error: cannot modify const member `x`