**Core Concept**
DNA fragment separation is a fundamental technique in molecular biology, enabling researchers to analyze the size and sequence of DNA molecules. This process relies on the principle of size exclusion, where smaller DNA fragments can pass through tiny pores, while larger fragments are retained. The technique is crucial in applications such as DNA sequencing, genetic engineering, and forensic analysis.

**Why the Correct Answer is Right**
The correct technique for DNA fragment separation is **Electrophoresis**. In this process, a mixture of DNA fragments is loaded onto a gel matrix, which is placed in an electric field. The negatively charged DNA fragments migrate towards the positive electrode, with smaller fragments moving faster and farther than larger ones. This separation is based on the size of the DNA fragments, allowing researchers to analyze and compare their lengths. The most commonly used type of electrophoresis for DNA fragment separation is **Agarose Gel Electrophoresis**.

**Why Each Wrong Option is Incorrect**
**Option A:** **Chromatography** is a technique used for separating mixtures of substances based on their interactions with a stationary phase, but it is not suitable for DNA fragment separation. Chromatography relies on the principle of adsorption or partitioning, which is not applicable to DNA fragments.

**Option B:** **Centrifugation** is a method used to separate particles of different densities or sizes by spinning them at high speeds. While centrifugation can separate DNA fragments based on their density, it is not as effective as electrophoresis for separating fragments of varying sizes.

**Option C:** **Ultracentrifugation** is a type of centrifugation that uses high-speed centrifuges to separate particles based on their density and size. Like centrifugation, ultracentrifugation is not the most effective method for DNA fragment separation, and it is not commonly used for this purpose.

**Clinical Pearl / High-Yield Fact**
A key factor to remember when performing DNA fragment separation by electrophoresis is that the size of the DNA fragments is inversely proportional to the distance they travel in the gel. This means that smaller DNA fragments will migrate farther from the starting point, while larger fragments will remain closer to the origin.

**Correct Answer: C. Electrophoresis**