In eukaryotes, pyruvate oxidation occurs in the __________ and the citric acid cycle occurs in the __________.

The correct answer is a) cytoplasm; mitochondrial matrix.

In eukaryotic cells, after glycolysis occurs in the cytoplasm, pyruvate is transported into the mitochondria. There, pyruvate undergoes oxidation to form acetyl-CoA, a crucial step known as pyruvate oxidation. This process takes place in the mitochondrial matrix.

Following this, the citric acid cycle (also known as the Krebs cycle) also occurs in the mitochondrial matrix. During this cycle, acetyl-CoA is further oxidized to produce energy carriers such as NADH and FADH₂, along with ATP. This cycle plays a key role in cellular respiration, allowing for the extraction of energy from nutrients.