What is the primary symptom of Parkinson's disease?

The primary symptom of Parkinson's disease is characterized by resting tremors and rigidity. This neurological disorder primarily affects movement control, leading to specific motor symptoms that are hallmark indicators of the condition. Resting tremors typically occur when the patient is relaxed and not engaged in any voluntary movement, while rigidity results in increased muscle tone and stiffness, making it difficult for individuals to initiate and execute movements smoothly.

These symptoms stem from the degeneration of dopamine-producing neurons in a part of the brain called the substantia nigra. As dopamine is crucial for coordinating movement, its loss leads to the motor disturbances seen in Parkinson's disease.

In contrast, severe memory loss is more associated with cognitive disorders like Alzheimer's disease, auditory hallucinations are more prevalent in psychiatric conditions, and loss of sensation can occur in various neurological conditions but is not indicative of Parkinson's disease specifically. Thus, resting tremors and rigidity serve as the primary and most recognizable features of Parkinson's, making this the correct answer.