If $A=\{1,2,3,4\},B=\{3,4,5,6\},C=\{5,6,7,8\}$ and $D=\{7,8,9,10\}$ Find $B\cup C$

Question

$\begin{array}{1 1}(A)\;\{3,4,5,6,7,8\}\\(B)\;\{3,4,5\}\\(C)\;\{5,6,8\}\\(D)\;\{7,8\}\end{array}$