**Core Concept**
The question tests the understanding of bioluminescence and its application in molecular biology. Bioluminescence is a process where a molecule reacts with oxygen to produce light, often used as a marker in genetic studies. In this case, firefly luciferase is an enzyme that catalyzes the production of light in the presence of oxygen.

**Why the Correct Answer is Right**
Firefly luciferase is a bioluminescent enzyme that produces light when it reacts with its substrate, luciferin, and oxygen. This reaction results in the production of oxyluciferin and light energy. The presence of luciferase in the firefly plant will lead to the emission of light in the dark, making it visible. On the other hand, GFP (Growth Fluoro Protein) is a fluorescent protein that emits light when excited by a specific wavelength of light, but it does not produce light spontaneously like luciferase.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not relevant to the question, as it does not describe a bioluminescent or fluorescent process.
**Option B:** GFP (Growth Fluoro Protein) is a fluorescent protein, not bioluminescent, and requires external excitation to emit light.
**Option C:** This option is not a correct description of the expected outcome.

**Clinical Pearl / High-Yield Fact**
Bioluminescence is a useful tool in molecular biology for studying gene expression and protein activity in real-time. Firefly luciferase is commonly used as a reporter gene to monitor gene expression and track protein activity in living organisms.

**Correct Answer:** C.