Which of the following class definitions defines a legal abstract class?

Select one:

A$.$ class A $\{$ abstract void unfinished $()\}\}$

B$.$ public class abstract A $($ abstract vold unfinished$()$; $\}$

C$.$ abstract class $A\{$ abstract void unfinished$()$; $\}$

D$.$ class A $\{$ abstract void unfinished$()$; $\}$