**Core Concept**
The concept being tested is the avoidance of first-pass hepatic metabolism through non-invasive routes of drug administration, particularly in the context of sustained-release preparations that maintain therapeutic drug levels for extended periods.

**Why the Correct Answer is Right**
Transdermal drug administration involves applying a drug preparation to the skin, where it is slowly absorbed into the bloodstream. This route bypasses the first-pass effect, which occurs when orally administered drugs are metabolized by the liver before reaching systemic circulation. Transdermal delivery systems, such as patches, are designed to release drugs slowly over an extended period, typically up to seven days. This results in more stable plasma concentrations and improved therapeutic efficacy.

**Why Each Wrong Option is Incorrect**
**Option A:** Topical drug administration, while non-invasive, does not necessarily involve sustained-release formulations and may not avoid first-pass metabolism entirely.
**Option C:** Sublingual administration involves placing a drug under the tongue, where it is absorbed directly into the bloodstream, but this route is not typically associated with sustained-release formulations.
**Option D:** Oral administration is subject to first-pass metabolism, which can result in reduced bioavailability and a shorter duration of action.

**Clinical Pearl / High-Yield Fact**
When considering sustained-release formulations, remember that transdermal delivery systems can provide prolonged therapeutic effects, while avoiding the peak-and-valley fluctuations associated with shorter-acting preparations.

**✓ Correct Answer: B. Transdermal**