Which of the following is a common symptom of Parkinson's disease?

Resting tremor is a hallmark symptom of Parkinson's disease, often recognized as one of the classic motor features. This tremor occurs when the muscles are at rest and typically manifests as rhythmic shaking, often beginning in one hand. The presence of a resting tremor is generally used in conjunction with other symptoms, such as rigidity and bradykinesia, to help diagnose Parkinson's disease.

Other symptoms listed, such as visual and auditory agnosia, chorea, and socially inappropriate behavior, are not commonly associated with Parkinson's. Visual and auditory agnosia pertains more to neurological conditions involving higher cognitive processing areas, while chorea is more characteristic of disorders such as Huntington's disease. Socially inappropriate behavior is often linked to different psychiatric conditions or dementia rather than Parkinson's. Thus, the presence of a resting tremor stands out as a key and defining sign of Parkinson's disease.