The correct answer is: B. the members of Ancestor will be included only once in Descendant.
When a class inherits from another class, the members of the base class are included in the derived class. This is called inheritance. The members of the base class are accessible in the derived class, and they can be overridden or extended.
In the code class Descendant : virtual public Ancestor, the class Descendant inherits from the class Ancestor. This means that all of the members of the class Ancestor are included in the class Descendant. The members of the class Ancestor are only included once in the class Descendant, even though they are accessible in both classes.
The other options are incorrect. Option A is incorrect because the members of the base class are only included once in the derived class. Option C is incorrect because the members of the derived class are not included in the base class. Option D is incorrect because the members of the base class are included in the derived class, but they are not included more than once.