The correct statement about the TCA (tricarboxylic acid) cycle is option 'C' - it occurs in the mitochondrial matrix. Here is a detailed explanation of why this statement is true:

1. Overview of the TCA Cycle:
The TCA cycle, also known as the citric acid cycle or Krebs cycle, is a series of enzymatic reactions that occur in the mitochondria of eukaryotic cells. It is an essential metabolic pathway that plays a central role in the aerobic respiration of carbohydrates, fats, and proteins.

2. Location of the TCA Cycle:
The TCA cycle takes place in the mitochondrial matrix, which is the innermost compartment of the mitochondria. The mitochondrial matrix contains the enzymes and cofactors required for the TCA cycle reactions to occur.

3. Structure of Mitochondria:
Mitochondria are double-membraned organelles found in most eukaryotic cells. They have an outer membrane that is permeable to small molecules and an inner membrane that is highly folded to form structures called cristae. The space between the inner and outer membranes is known as the intermembrane space, while the innermost compartment enclosed by the inner membrane is the mitochondrial matrix.

4. Enzymes and Reactions of the TCA Cycle:
The TCA cycle consists of a series of eight enzymatic reactions that oxidize acetyl-CoA, a two-carbon molecule derived from various fuel sources, to produce energy-rich compounds such as NADH and FADH2. These energy carriers participate in subsequent steps of cellular respiration, leading to the production of ATP through oxidative phosphorylation.

5. Importance of the Mitochondrial Matrix:
The mitochondrial matrix provides an ideal environment for the TCA cycle to occur. It contains the necessary enzymes, such as citrate synthase, isocitrate dehydrogenase, α-ketoglutarate dehydrogenase, and succinyl-CoA synthetase, which catalyze the various reactions of the cycle. Additionally, the matrix houses the coenzymes and cofactors required for the enzymatic reactions, including NAD+, FAD, and Coenzyme A.

In conclusion, the TCA cycle occurs in the mitochondrial matrix, making option 'C' the correct statement. The mitochondrial matrix provides the necessary enzymes and cofactors for the cycle to take place, playing a crucial role in cellular respiration and ATP production.