The correct answer is option 'C' - 20 ATP molecules are generated from the oxidation of one molecule of glucose in the TCA (Tricarboxylic Acid) cycle. Let's break down the steps involved in the TCA cycle to understand how this occurs.

1. Step 1: Conversion of Pyruvate to Acetyl-CoA
- In the presence of oxygen, pyruvate, which is the end product of glycolysis, enters the mitochondria.
- Each pyruvate molecule is converted to acetyl-CoA through decarboxylation, releasing one molecule of CO2.
- This step yields one molecule of NADH (Nicotinamide Adenine Dinucleotide) and one molecule of acetyl-CoA.

2. Step 2: Acetyl-CoA Enters the TCA Cycle
- Acetyl-CoA enters the TCA cycle by combining with oxaloacetate to form citrate, a six-carbon compound.
- The conversion of acetyl-CoA to citrate is catalyzed by the enzyme citrate synthase.

3. Step 3: Series of Reactions in the TCA Cycle
- Through a series of reactions, citrate is converted into isocitrate, α-ketoglutarate, succinyl-CoA, succinate, fumarate, and finally malate.
- Each of these reactions involves the release of CO2 and the generation of NADH or FADH2 (Flavin Adenine Dinucleotide).

4. Step 4: Energy Production
- The NADH and FADH2 molecules produced in the TCA cycle are utilized in the electron transport chain, which is located in the inner mitochondrial membrane.
- As the electrons pass through the electron transport chain, ATP is generated through oxidative phosphorylation.
- Each NADH molecule generates approximately 2.5 ATP molecules, while each FADH2 molecule generates approximately 1.5 ATP molecules.

5. Step 5: Total ATP Production
- From one molecule of glucose, two molecules of pyruvate are produced.
- Each pyruvate enters the TCA cycle and generates three molecules of NADH and one molecule of FADH2.
- Therefore, the total ATP production from the oxidation of one molecule of glucose in the TCA cycle is:
- NADH: 3 × 2.5 = 7.5 ATP
- FADH2: 1 × 1.5 = 1.5 ATP
- In addition, two molecules of ATP are generated directly during glycolysis.
- Adding up the ATP from NADH, FADH2, and glycolysis, we get a total of 7.5 + 1.5 + 2 = 11 ATP.
- However, for each NADH molecule generated in the cytoplasm during glycolysis, it is transported into the mitochondria, resulting in the loss of one ATP in the process.
- Therefore, the net ATP production from the oxidation of one molecule of glucose in the TCA cycle is 11 - 1 = 10 ATP.

Hence, the correct answer is option 'C' - 20 ATP.