**Core Concept**
The Iodine:Particle ratio is a measure of the concentration of iodine in a radiographic contrast agent relative to the concentration of particles, such as barium sulfate or iodinated gelatin, that are used to enhance the contrast of images. This ratio is critical in determining the optimal composition of contrast agents for various imaging modalities, including radiography and CT scans.

**Why the Correct Answer is Right**
The Iodine:Particle ratio is maximum for **Carmellose**. Carmellose is a type of carboxymethylcellulose, a polysaccharide that is commonly used as a thickening agent in contrast agents. Its high iodine content and high molecular weight make it an ideal component for achieving a high Iodine:Particle ratio. This is because carmellose can bind a large amount of iodine, thereby increasing the overall iodine concentration in the contrast agent.

**Why Each Wrong Option is Incorrect**
**Option A:** is incorrect because it does not specify the type of particle used in the contrast agent, making it impossible to determine the Iodine:Particle ratio.
**Option B:** is incorrect because it is a type of thickening agent that is not commonly used in contrast agents, and its iodine content is not well established.

**Clinical Pearl / High-Yield Fact**
When selecting a contrast agent, it is essential to consider the Iodine:Particle ratio to ensure optimal image quality and minimize the risk of adverse reactions. A high Iodine:Particle ratio is generally associated with better image quality and lower risk of complications.

**Correct Answer: C. Carmellose**