An older adult with suspected Parkinson's disease has a "challenge test" performed in order to confirm the diagnosis. The nurse understands that a "challenge test" will demonstrate which of the following?

A. Dramatic improvement in tremor only after administration of levodopa: Levodopa improves more than just tremor; it also alleviates rigidity, bradykinesia, and other motor symptoms. Improvement in tremor alone would not confirm the diagnosis. B. Dramatic improvement in gait only after administration of levodopa: Gait improvement may occur, but it is not the sole indicator of Parkinson’s disease. A comprehensive response—including better movement fluidity and reduced rigidity—provides stronger diagnostic confirmation. C. Immediate reversal of all symptoms of Parkinson’s disease after administration of levodopa: Complete or immediate reversal does not occur, even during a challenge test. The response to levodopa typically develops over a short time and indicates the presence of dopaminergic neuron deficiency, not a total cure. D. Dramatic improvement of symptoms of Parkinson’s disease after administration of levodopa: The levodopa challenge test helps confirm Parkinson’s disease when motor symptoms significantly improve after administration. This response supports the diagnosis by demonstrating that dopamine replacement alleviates motor dysfunction.