## **Core Concept**
The core concept being tested here relates to the legal and medical definition of fetal viability. Fetal viability refers to the point at which a fetus can survive outside the womb with the aid of medical technology. This concept is crucial in obstetrics and medical law.

## **Why the Correct Answer is Right**
The correct answer, **D. 28 weeks**, is based on the medical and legal definition of fetal viability. According to the World Health Organization (WHO) and various medical guidelines, a fetus is generally considered capable of independent existence with medical assistance at around 28 weeks of gestation. This is because, at this stage, the lungs are usually mature enough to support breathing, and other vital organs are sufficiently developed.

## **Why Each Wrong Option is Incorrect**
- **Option A:** Without specifying the gestational age, it's impossible to evaluate its correctness directly, but given that typical viability thresholds are discussed in terms of weeks, an unspecified option is likely incorrect or incomplete.
- **Option B:** and **Option C:** Similarly, without specific gestational ages provided for these options, it's not possible to directly assess their accuracy. However, given that fetal viability is a well-defined concept around 28 weeks, options that do not align with this are likely incorrect.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that fetal viability is a critical concept in both medicine and law, particularly in the context of abortion and neonatal care. The age of viability has decreased over the years due to advances in medical technology. However, **28 weeks** remains a commonly cited threshold for independent existence with medical assistance.

## **Correct Answer: D. 28 weeks.**