A.class Widget{Sprocket s;};class Gadget extends Widget{Spring s;}
B.class Widget{};class Gadget extends Widget{Spring s1; Sprocket s2;}
C.class Widget{Sprocket s1; Spring s2;};class Gadget extends Widget{}
D.class Gadget{Spring s;};class Widget extends Gadget{Sprocket s;}
E.class Gadget{};class Widget extends Gadget{Sprocket s1; Spring s2;}
F.class Gadget{Spring s1; Sprocket s2;};class Widget extends Gadget{}