## Core Concept
The question pertains to the concept of independent assortment in genetics, which is a fundamental principle of Mendelian inheritance. Independent assortment refers to the random distribution of maternal and paternal chromosomes during gamete formation, specifically during meiosis I. This process increases genetic diversity by creating unique combinations of chromosomes in offspring.

## Why the Correct Answer is Right
Independent assortment occurs at the **tetrad level** or during the **diploid (2n) stage** of cell division, specifically during meiosis I when homologous pairs of chromosomes line up at the metaphase plate. Each pair of chromosomes consists of one maternal and one paternal chromosome, and the orientation of each pair is random. This randomness leads to the independent assortment of chromosomes, meaning that the combination of chromosomes in each gamete is unique. The correct answer, , reflects this concept.

## Why Each Wrong Option is Incorrect
- **Option A:** This option is incorrect because independent assortment does not occur at the level of individual chromatids; rather, it involves the separation of entire chromosomes.
- **Option B:** This option is incorrect because while crossing over does occur during meiosis I and contributes to genetic diversity, it is not the level at which independent assortment of chromosomes occurs.
- **Option D:** This option is incorrect because independent assortment is specifically related to the distribution of chromosomes, not the genes themselves.

## Clinical Pearl / High-Yield Fact
A key point to remember is that independent assortment, along with crossing over, significantly contributes to genetic diversity. This concept is crucial for understanding inheritance patterns and is often tested in the context of genetic diseases and syndromes.

## Correct Answer Line
**Correct Answer: C. Tetrad level**