What is a polymorphic variable in $\backslash (\backslash$mathrm$\{$C$\}++\backslash )?$ A pointer or reference variable of an abstract class type that is able to refer to objects of that class and objects of any of its descendants' classes. A pointer or reference variable of a class type that is able to point to objects of that class and objects of any of its descendants' classes. A pointer or reference variable of a class that can point to objects of its own class type only. A pointer variable of a class type that is able to point to objects of that class and objects of any of its descendants or ancestors' classes.