Correct Answer - D
There are minimum five carbon atoms in ketons which will show chain isomerism
(i) ` CH _ 3 - underset (O ) underset ( "||")C - CH _ 2 - CH _ 2 - CH _ 3 `
(ii) ` CH _ 3 -underset (O ) underset ("||")C - underset ( CH_ 3 ) underset ( |) ( CH ) - CH _ 3 `