Why Would Levodopa Be Administered Instead of Oral DA to Help

Why would Levodopa be administered instead of oral DA to help treat Parkinson's disease?

A) Bioavailability of oral DA is limited because it does not cross the blood-brain barrier.
B) DA would be rapidly metabolized by catechol-O-methyltransferase (COMT) in the gastrointestinal (GI) tract,reducing bioavailability.
C) Levodopa causes less adverse effects than oral DA would.
D) Levodopa and oral DA are typically prescribed equally to treat Parkinson's disease.