A hallmark symptom of Parkinson's disease includes which of the following?

A hallmark symptom of Parkinson's disease is a resting tremor. This tremor typically occurs when the muscles are relaxed and can often be described as a "pill-rolling" motion of the hands. It is important to note that this tremor usually diminishes or may even disappear with purposeful movement, which distinguishes it from other types of tremors.

Parkinson's disease is primarily characterized by a combination of motor symptoms, including bradykinesia (slowness of movement), rigidity (muscle stiffness), and postural instability, alongside the resting tremor. The presence of these features helps clinicians in diagnosing the disease.

Other options do not align with the primary symptoms associated with Parkinson's disease. Ataxia refers to impaired coordination and balance that is more consistent with cerebellar disorders. Expressive aphasia involves difficulties in speech production, which is related to language processing areas in the brain, not typically seen in Parkinson’s. Seizures are sudden electrical disturbances in the brain and are not a common feature of this condition. Together, these distinctions underline why the resting tremor is specifically recognized as a key symptom of Parkinson's disease.