To answer this question, you need to understand the concept of initializing variables from existing variables.
Let's go through each option to understand why it is correct or incorrect:
Option A) Virtual Function - Virtual functions are used to achieve polymorphism in object-oriented programming. They are not used for initializing variables from existing variables, so this option is incorrect.
Option B) Namespaces - Namespaces are used to organize code into logical groups and prevent naming conflicts. They are not used for initializing variables from existing variables, so this option is incorrect.
Option C) Copy Constructor - A copy constructor is a special constructor that creates a new object by initializing it with an existing object of the same class. This is the correct option because it allows you to initialize a newly declared variable from an existing variable.
Option D) None of the Above - This option is incorrect because the correct answer is option C, copy constructor.
The correct answer is option C) copy constructor. This option is correct because it allows you to initialize a newly declared variable from an existing variable.