Lionel has parkinson's disease and has difficulty starting motor movements because the neurons involved with dopamine activity are

The answer to this question would be: a. dying off.

Parkinson's disease is caused by the cell in the substantia nigra of the midbrain is dying one by one. This cause a decline of dopamine produced, make the motoric movement become harder. The reason why the cell die is not well understood, so the treatment is more focused on increasing dopamine transmitter in the brain.