**Core Concept**
The question is testing the limits of fetal viability, which refers to the stage at which a fetus can survive outside the uterus with or without medical assistance. This concept is crucial in obstetrics and is often used to guide decisions regarding the continuation or termination of a pregnancy.

**Why the Correct Answer is Right**
Fetal viability is determined by the development of the fetal lungs, heart, and other vital organs. The key factor is the presence of surfactant in the fetal lungs, which reduces the surface tension and allows for easier expansion during breathing. The development of surfactant production is a critical milestone in fetal lung maturation, and it typically occurs around 24-28 weeks of gestation. This period is often referred to as the "viability window." Before this window, the fetus is not considered viable, and the likelihood of survival outside the uterus is extremely low.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it is too early for fetal viability. At 20 weeks, the fetus is still in a critical stage of development, and the lungs are not yet mature enough to support life outside the uterus.
**Option B:** This option is incorrect because it is still within the range of fetal viability. While the fetus is closer to being viable, it is not yet considered a strong candidate for survival outside the uterus.
**Option C:** This option is incorrect because it is too late for fetal viability. After 32 weeks, the fetus is typically considered viable and can survive outside the uterus with medical assistance.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that the viability window can vary depending on the presence of certain medical conditions, such as prematurity or congenital anomalies. Additionally, the development of fetal lung maturity tests, such as the lecithin-sphingomyelin (L/S) ratio, can help guide decisions regarding fetal viability.

**Correct Answer:** C. 32 weeks.