<P> An association role is given end of an association and describes the role of the corresponding class . For example, a "subscriber" role describes the way instances of the class "Person" participate in a "subscribes - to" association with the class "Magazine". Also, a "Magazine" has the "subscribed magazine" role in the same association . Association role multiplicity describes how many instances correspond to each instance of the other class of the association . Common multiplicities are "0...1", "1...1", "1...*" and "0...*", where the "*" specifies any number of instances . </P> <P> There are many categories of classes, some of which overlap . </P> <P> In a language that supports inheritance, an abstract class, or abstract base class (ABC), is a class that cannot be instantiated because it is either labeled as abstract or it simply specifies abstract methods (or virtual methods). An abstract class may provide implementations of some methods, and may also specify virtual methods via signatures that are to be implemented by direct or indirect descendants of the abstract class . Before a class derived from an abstract class can be instantiated, all abstract methods of its parent classes must be implemented by some class in the derivation chain . </P> <P> Most object - oriented programming languages allow the programmer to specify which classes are considered abstract and will not allow these to be instantiated . For example, in Java, C#and PHP, the keyword abstract is used . In C++, an abstract class is a class having at least one abstract method given by the appropriate syntax in that language (a pure virtual function in C++ parlance). </P>

Which of the following may be a part of a class definition