public abstract class Shape { private int x; private int y; public abstract void draw(); public void setAnchor(int x, int y) { this.x = x; this.y = y; } } 下列哪一个类是对Shape的正确引用（ ）。
选项：

A:public class Circle implements Shape { private int radius; }
B:public abstract class Circle extends Shape { private int radius; }
C:public class Circle extends Shape { private int radius; public void draw(); }
D:public abstract class Circle implements Shape { private int radius; public void draw(); }