The correct statement regarding a carbonyl compound with a hydrogen atom on its alpha carbon, is given by the option D.
"A carbonyl compound with a hydrogen atom on its alpha-carbon rapidly equilibrates with its corresponding enol and this process is known as keto-enol tautomerism."
For example, the keto enol tautomerism for acetaldehyde is as shown.
CH3CHO⇌CH2=CHOH
The inter conversion of the two forms (keto and enol) involves the movement of an alpha hydrogen and the shifting of bonding electrons.