QUIZ 8
        (Z)

       |+/-|            (A)             (B)
         |  
         |             2      2        2    2
        |+|        (-a) + (-b)      - a  + b
       /   \ 
      /     \
   |^|       |^|               (C)
  /   \     /   \
 /     \   /     \             2   2
a       2 b       2       - ( a + b )


(Z)  -->  (A) | (B) | (C) ?
(Z) -->