**Core Concept**
The question is testing the knowledge of the enzyme responsible for the complete oxidation of glucose to carbon dioxide (CO2) and water (H2O) in cellular respiration. This process involves the breakdown of glucose to produce energy in the form of ATP.

**Why the Correct Answer is Right**
The correct answer is **Pyruvate Dehydrogenase (PDH)**. Pyruvate Dehydrogenase is a multi-enzyme complex that catalyzes the conversion of pyruvate, a product of glycolysis, into acetyl-CoA. Acetyl-CoA then enters the citric acid cycle (also known as the Krebs cycle or tricarboxylic acid cycle), where it is completely oxidized to produce CO2 and H2O, releasing a significant amount of ATP through the electron transport chain. Pyruvate Dehydrogenase is a crucial enzyme in the link between glycolysis and the citric acid cycle.

**Why Each Wrong Option is Incorrect**
* **Option A:** This is a placeholder for an incorrect option. However, a common distractor could be the enzyme Pyruvate Kinase, which is involved in glycolysis but not the complete oxidation of glucose.
* **Option B:** This is another placeholder. A possible distractor could be the enzyme Glyceraldehyde-3-Phosphate Dehydrogenase, which is also involved in glycolysis but not the complete oxidation of glucose.
* **Option C:** This is another placeholder. A possible distractor could be the enzyme Citrate Synthase, which is involved in the citric acid cycle but not the initial step of complete glucose oxidation.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that Pyruvate Dehydrogenase is a multi-enzyme complex that requires thiamine pyrophosphate (TPP), lipoic acid, and coenzyme A for its activity. Deficiencies in these cofactors can lead to disorders such as lactic acidosis.

**Correct Answer:** C. Pyruvate Dehydrogenase.