**Core Concept**
Sex chromatin testing is a method used to determine the genetic sex of an individual, particularly in cases where the sex chromosomes are not clearly identifiable. This technique relies on the presence of specific chromatin structures that are associated with the sex chromosomes.

**Why the Correct Answer is Right**
Sex chromatin testing is based on the concept of Barr bodies, which are small, darkly staining regions of chromatin that are found in the nucleus of cells. Barr bodies are formed when one of the two X chromosomes in a female cell inactivates, resulting in a compact, heterochromatic structure. The presence of one or more Barr bodies in a cell is indicative of the presence of at least one X chromosome, and therefore, a female sex chromosomal pattern. This technique is particularly useful in cases where the sex of an individual is ambiguous or unknown.

**Why Each Wrong Option is Incorrect**
**Option A:** is incorrect because it does not describe a method related to sex chromatin testing.
**Option B:** is incorrect because while sex chromatin testing is a method for determining sex, it is not a form of genetic testing, but rather a cytogenetic test.
**Option C:** is incorrect because it refers to a different genetic test, not sex chromatin testing.

**Clinical Pearl / High-Yield Fact**
Barr bodies are not unique to females; they can also be found in individuals with more than one X chromosome, such as in cases of Klinefelter syndrome (47,XXY).

**Correct Answer: C. Barr bodies.**