If $A$ and $B$ both contain same number of elements and are finite sets then

• A

  $n(A\cup B)=n(A\cap B)$

• B

  $n(A~B)=n(B~A)$

• C

  $n\left(A\mathrm{\Delta }B\right)=n\left(B\right)$

• D

  $n(A-B)=n\left(A\right)$