Tìm $ A\backslash B $ , biết $ A=\left\{ 1;2;3;4;6;9 \right\};\,\,B=\left\{ 2;3 \right\} $
A. $ A\backslash B=\left\{ 6;9 \right\} $
B. $ A\backslash B=\left\{ 1;2;3;4 \right\} $
C. $ A\backslash B=\left\{ 2;3 \right\} $
D. $ A\backslash B=\left\{ 1;4;6;9 \right\} $