If A={3,6,9,12,15,18,21},B={4,8,12,16,20},C={2,4,6,8,10,12,14,16},D={5,10,15,20} (i) A-B

Question

$\begin{array}{1 1}(A)\;\{3,6,9,12,15,18,21\}&(B)\;\{3,6,9,15,18,21\}\\(C)\;\{4,8,12,16,60\}&(D)\;\phi\end{array} $