This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Psychiatry
Delirium is distinguished from dementia by the presence of 
Select and explain. 
A. Impaired judgment, B. Impaired memory, C. Clouding of consciousness, D. Thought disorder
C: Clouding of consciousness
Answer: C: Clouding of consciousness 
Explanation: Ans.C. Clouding of consciousnessThe hallmark of delirium is fluctuation in the level of consciousness.Periods of lucency may be interspersed with periods of marked unresponsiveness.Another distinguishing feature is that the onset of delirium usually occurs within hours or days, whereas the onset of dementia may be insidious throughout weeks to months.