Final answer:
The fastest route of medication administration to be absorbed is intravenous (D).
Step-by-step explanation:
The fastest route of medication administration to be absorbed is intravenous (D). When a drug is administered intravenously, it directly enters the bloodstream, bypassing the need for absorption through the GI tract or muscle tissue. This allows for rapid and complete delivery of the drug into the systemic circulation, resulting in higher plasma levels compared to other routes of administration.