Final answer:
The most rapid rate of medication absorption is provided by the intravenous route.
Step-by-step explanation:
The most rapid rate of medication absorption is provided by the intravenous route. When a drug is administered intravenously, it is directly delivered into the bloodstream, bypassing the need for absorption from the gastrointestinal tract. This results in immediate and high plasma levels of the drug.
On the other hand, oral administration involves the drug being taken by mouth and absorbed through the digestive tract. It takes longer for the drug to be absorbed into the bloodstream, resulting in slower and lower plasma levels compared to intravenous administration.
Hence, the correct answer is C. Vein.