All but $$33$$ can be represented as required, as shown below.  A. $$43=1+42$$  B. $$33$$  C. $$23=2+21$$  D. $$13=6+7$$ 
The product of two whole numbers is $$42$$. Their sum \emph{cannot} be． 
  * $$43$$ 
  * $$33$$ 
  * $$23$$ 
  * $$13$$ 