Final answer:
The most appropriate and convenient route of administration for an antimicrobial to treat a systemic infection at home is oral (A). This route allows for easy self-administration and absorption through the gastrointestinal tract.
Step-by-step explanation:
The question is asking which route of administration would be most appropriate and convenient for self-administration at home when treating a systemic infection with an antimicrobial. For home administration, the oral route is generally preferred for its ease and convenience. Drugs that are administered orally are preferred because they can be taken at home without the need for professional assistance, unlike intravenous, intramuscular, or subcutaneous injections that typically require healthcare settings. Moreover, oral medications are designed to be absorbed through the gastrointestinal (GI) tract into the bloodstream, making them effective for systemic infections. Nevertheless, some drugs may not be easily absorbed or are intended for local effects. In such cases, they might be administered topically or by parenteral routes in clinical settings. Therefore, the correct answer is A. oral.