If $A=\{3,5,7,9,11\},B=\{7,9,11,13\},C=\{11,13,15\}$ and $D=\{15,17\}$.Find $A\cap B$

Question

$\begin{array}{1 1}(A)\;\{3,5,7,9,11\}&(B)\;\{7,9,11,13\}\\(C)\;\{7,9\}&(D)\;\{3,5,7,9,11,13\}\end{array} $