A patient with acute psychosis, who is on haloperidol 20mg/day for last 2 days,has an episode characterized by tongue protrusion,oculogyric crisis,torticollis and abnormal posture of limbs and trunk without loss of consciousness for 20 minutes before presenting to the emergency department.This improved within a few minutes after administration of diphenhydramine.The most likely diagnosis is:

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