**Core Concept**
The operon model is a fundamental concept in molecular biology that describes the regulation of gene expression in prokaryotes. It explains how a group of genes that encode enzymes for a specific metabolic pathway are controlled by a single regulatory unit, known as an operon.

**Why the Correct Answer is Right**
The operon model was first proposed by François Jacob and Jacques Monod in 1961, who demonstrated that the lac operon in E. coli regulates the expression of genes involved in lactose metabolism. The operon consists of a promoter region, an operator region, and a series of structural genes that encode enzymes for lactose metabolism. The lac repressor protein binds to the operator region, blocking transcription of the structural genes, while the presence of lactose induces the expression of the lac operon by binding to the repressor protein and preventing its binding to the operator.

**Why Each Wrong Option is Incorrect**
**Option A:** The incorrect statement is that the operon model was elucidated by an unknown researcher. However, as mentioned earlier, the operon model was first proposed by François Jacob and Jacques Monod.
**Option B:** The incorrect statement is that the operon model was elucidated by a researcher who studied eukaryotes. The operon model is specific to prokaryotes, such as E. coli.
**Option C:** The incorrect statement is that the operon model was elucidated by a researcher who studied the regulation of gene expression in plants. While plants have similar regulatory mechanisms, the operon model was first described in prokaryotes.

**Clinical Pearl / High-Yield Fact**
The operon model has significant implications for understanding the regulation of gene expression in prokaryotes, and has been applied to the study of various metabolic pathways. Additionally, the concept of gene regulation through repressor proteins has been extended to eukaryotes, where similar mechanisms are used to control gene expression.

**Correct Answer: C. Jacob and Monod.