A block of mass $2 \mathrm{~kg}$ is held over a vertical spring with spring unstretched. Suddenly, if block is left free, maximum compression of spring is [spring constant $K=200 \mathrm{~N} / \mathrm{m}]:$
(A) $0.2 \mathrm{~m}$
(B) $0.1 \mathrm{~m}$
(C) $0.4 \mathrm{~m}$
(D) $0.05 \mathrm{~m}$