Why Would Adding Carbidopa to Levodopa Increase Levodopa Bioavailability

Why would adding carbidopa to levodopa increase levodopa bioavailability?

A) The adjuvant inhibits the production of acetylcholinesterase (AChE) ,which metabolizes levodopa in the body.
B) Monoamine oxidase (MAO) is able to metabolize levodopa faster than the levodopa can be absorbed by the body,and the adjuvant helps slow down this process.
C) The adjuvant inhibits decarboxylase,which metabolizes levodopa in the GI tract and peripheral tissues.
D) COMT metabolizes levodopa in the GI tract faster than the levodopa can be absorbed by the body,and the adjuvant inhibits the production of COMT.