Considere os conjuntos $A=\left\{1,\left\{1\right\},2\right\}$ e $B=\left\{1,2,\left\{2\right\}\right\}$ e as cinco afirmações:

1. I. $A-B=\left\{1\right\}$
   

2. II. $\left\{2\right\}\subset \left(B-A\right)$
   

3. III. $\left\{1\right\}\subset A$
   

4. IV. $A\cup B=\left\{1,2,\left\{1,2\right\}\right\}$
   

5. V. $B-A=\left\{\left\{2\right\}\right\}$
   

Logo,