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    Question

    In C++, how is abstraction primarily achieved when

    defining a class that cannot be instantiated directly but serves as a blueprint for derived classes?
    A By making all member variables `private`. Correct Answer Incorrect Answer
    B By using the `virtual` keyword for all methods. Correct Answer Incorrect Answer
    C By declaring at least one pure virtual function (e.g., `virtual void func() = 0;`). Correct Answer Incorrect Answer
    D By making the constructor `protected`. Correct Answer Incorrect Answer
    E By using the `abstract` keyword (which does not exist in C++). Correct Answer Incorrect Answer

    Solution

    o In C++, a class is considered an abstract base class if it has at least one pure virtual function. A pure virtual function is declared by assigning = 0 to it in the base class's declaration (e.g., virtual void func() = 0;). o Abstract classes cannot be instantiated directly. They serve as interfaces or blueprints, forcing derived classes to provide implementations for all pure virtual functions to become concrete (instantiable).

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