This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Parkinsonism, Subject name: Medicine
[{'content': 'Earliest feature of parkinsonism? \nSelect and explain. \nA. Anosmia, B. Rigidity, C. Postural instability, D. Freezing', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. (a) AnosmiaRef: Harrison 19th ed. / 2609Non-motor symptoms may precede motor symptoms of Parkinsons diagnosis by years. The most recognizable early symptoms include:* Loss of sense of smell, constipation* REM behavior disorder* mood disorders* Orthostatic hypotensionSubsequently Motor Features Appear1. Tremors (resting 4-6 Hz)2. Rigidity3. Bradykinesia4. Good Response to levodopa', 'role': 'assistant'}]