The correct option is D RCH2NO2
For a compound to exhibit tautomerism, presence of α-hydrogen is neccessary at its sp3 hybridised ⍺-C atom. This is satisfied only by RCH2NO2. Hence it will show tautomerism.
(a,b,c) do not contain acidic α−hydrogen at its sp3 hybridised ⍺-C atom and hence it will not show tautomerism.