Answer:
a.Parkinson's disease
Explanation:
Dopamine is a neurotransmitter who's function is to be the body's reward center "happy hormone" and it is also involved in motor control.
For unknown reasons in the elderly, dopamine is lost when the dopamine-producing nerve cells die in the basal ganglia and substanta nigra which results in movement problems such as, tremor, slowness of movement, stiffness, and balance problems.
This disease is called Parkinsons disease which is a progressive and degenerative disorder
