With the sudden onset of severe psychotic symptoms, the individual is said to be experiencing acute schizophrenia (精神分裂症). "Psychotic" means out of touch with reality, or unable to separate real from unreal experiences. Some people have only one such psychotic episode. Others have many episodes during a lifetime but lead relatively normal lives during interim periods. The individual with chronic (continuous or recurring) schizophrenia often does not fully recover normal functioning and typically requires long-term treatment, generally including medication, to control the symptoms. These symptoms may include hallucinations (幻觉), incoherence, delusions, lack of judgment, deterioration of the abilities to reason and feel emotion, and a lack of interaction between the patient and his environment. The hallucinations may be a visual, auditory, or tactile. Some chronic schizophrenic patients may never he able to function without assistance of one sort or another.

Which of the following is NOT a symptom of schizophrenia（）

A. Hallucinations.
B. Delusions.
C. Incoherence.
D. Vertigo.