To answer this question, you need to understand the concept of virtual functions in C++.

In C++, virtual functions are used to achieve runtime polymorphism. When a base class pointer points to a derived class object, and a virtual function is called using that pointer, the function in the derived class gets executed instead of the base class. This allows for dynamic binding of the function call based on the actual type of the object being pointed to.

Now, let's go through each option to understand why it is correct or incorrect:

Option A) virtual destructor - This option is correct. In C++, a virtual destructor is used to ensure that the destructor of the most derived class is called when deleting an object through a base class pointer. This is important when dealing with polymorphic objects to ensure that all resources are properly deallocated.

Option B) virtual constructor - This option is incorrect. In C++, constructors cannot be virtual. The constructor of a class is called automatically when an object is created, and it is determined statically at compile-time based on the type of the object being created.

Option C) Both A and B - This option is incorrect because option B is incorrect. Only option A, virtual destructor, exists in C++.

Option D) None of the Above - This option is incorrect. As explained above, option A, virtual destructor, exists in C++.

The correct answer is A) virtual destructor. This option is correct because a virtual destructor is used in C++ to ensure proper cleanup of resources when deleting objects through base class pointers.

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• Wrong explanation

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.

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• Wrong explanation