Final answer:
Delirium is a clouding of consciousness that develops quickly and can often be reversed, distinguishing it from dementia, amnesia, and syncope.
Step-by-step explanation:
A clouding of consciousness that develops over a short period of time and often can be reversed if its underlying cause is found is called: B) Delirium. Delirium is a rapid onset of confusion that creates a distorted mental state, characterized by a lack of awareness, difficulty in paying attention, delusions, and sometimes hallucinations. Unlike dementia, which is a chronic and progressive condition, delirium is usually a temporary and treatable condition. Identifying and treating the underlying cause can lead to a full recovery. Amnesia is a loss of memory, and syncope refers to fainting or a sudden, temporary loss of consciousness.