Once again thank you zenobia43
OK I am getting the picture now. Is it the same logic if it were ?:- May is either Parrot or Finch. I guess that wouldn't be the same logic would it?
And getting back to the old sortie of; Of A and B one is C and the other is D.Where A is either C or D and B is either C or D
If A is a colour can we only mark negatives against C and D as negative colours?
and vice versa for B,C,D?
A reminder of the real world.
BTW I wish you all a happy New Year from Scotland. Sing Auld Lang Syne wherever you are tonight.