A patient is being treated for Parkinson's disease and has been prescribed both levodopa (L-dopa) ...

A patient is being treated for Parkinson's disease and has been prescribed both levodopa (L-dopa) and carbidopa (Lodosyn). Why is this course of treatment most effective?
 
  A) Levodopa restores dopamine and carbidopa decreases peripheral breakdown of levodopa.
  B) Levodopa decreases the toxic effects of carbidopa to reduce the extrapyramidal reaction.
  C) Carbidopa increases the peripheral breakdown of levodopa to increase its effectiveness.
  D) Levodopa and carbidopa combined exacerbate abnormal voluntary movement to increase gait.