Patients with Parkinson's Disease Are Treated with L-DOPA, a Hydrophobic

Patients with Parkinson's disease are treated with L-DOPA, a hydrophobic precursor to dopamine, a hydrophilic neurotransmitter that is depleted in these patients. What is the most probable reason why these patients are given the precursor L-DOPA instead of dopamine?

A) L-DOPA is better at activating dopamine receptors than dopamine.
B) L-DOPA is more toxic than dopamine.
C) L-DOPA cannot cross the blood-brain barrier.
D) Dopamine cannot cross the blood-brain barrier.
E) Dopamine given orally could activate acetylcholine receptors.