**Core Concept**
The process of plaque formation in a virus is a critical step in the study of viral replication and cytopathic effects. It involves the formation of a visible, localized area of cell death in a monolayer of cells, resulting from the replication of a virus.

**Why the Correct Answer is Right**
Plaque formation is achieved by treating the infected cell culture with a nutrient agar overlay that restricts the spread of the virus. This process allows for the visualization of individual plaques, which are essentially areas of cell death caused by the virus. The agar overlay prevents the virus from spreading beyond the original infected cell, resulting in a clear boundary between the infected and uninfected areas. This method is essential for studying viral replication and determining the viral titer in a sample.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it doesn't describe a known method for plaque formation in viruses.
**Option B:** This option is incorrect because it doesn't relate to the process of plaque formation in viruses.
**Option C:** This option is incorrect because it's not a relevant method for studying viral replication and plaque formation.

**Clinical Pearl / High-Yield Fact**
When studying viral plaque formation, it's essential to remember that the agar overlay should be nutrient-poor to restrict viral spread and allow for the clear visualization of individual plaques.

**Correct Answer: C.**