## **Core Concept**
The question pertains to the properties of viruses, specifically their structure and composition. Viruses are obligate parasites that can be crystallized and have been found to possess certain characteristics similar to those of crystals.

## **Why the Correct Answer is Right**
The correct answer, , indicates that certain viruses have been isolated in crystalline form and have been found to be **crystallizable** and **non-living**. This is because viruses exhibit properties of both living and non-living things. When isolated in crystalline form, they do not exhibit metabolic processes or reproduce on their own, characteristics that define living organisms. Instead, they require a host cell to replicate. Their crystalline structure can be purified and isolated, similar to crystals of minerals or chemicals.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because it does not accurately describe the nature of viruses when isolated in crystalline form.
- **Option B:** This option is incorrect as it does not correctly represent the characteristics of viruses in crystalline form.
- **Option D:** This option is incorrect because it inaccurately describes viruses isolated in crystalline form.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the ability of viruses to be crystallized and their dependency on a host cell for replication highlight their unique position between living and non-living entities. This characteristic is crucial for understanding virology and the development of antiviral therapies.

## **Correct Answer:** .