riddle 9: none and nothing...  because nothing belongs to group a...  none belongs there to xD 
riddle 20: the sun... which is very often taken as a timepiece by itself (high noon = sun is straight up) and by definition is an uncountable number of atoms moving around and being flung out into space.  and since each atom could beconsided a part... and being bigger then earth itself, there could be none bigger 

--edit: wow... I rly just didn't expect this thread to go dead for 2 months... sorry for reviving it (of course, I suppose that is a fitting place for me right now anyway, huh? 

 )  
