A patient with acute psychosis, who is on haloperidol 20 mg/day for last two days, has an episode characterized by tongue protrusion, oculogyric crisis, stiffness and abnormal posture of limbs and trunk without loss of consciousness for last 20 minutes before presenting to casualty. This improved within a few minutes after administration of diphenhydramine HCI.The most likely diagnosis is -

• A. Tardive dyskinesia
• B. Neuroleptic malignant syndrome
• C. Acute dystonia
• D. Akathiosia