Before entering the Krebs cycle, the pyruvate is decarboxylated into

Explanation

Glycolysis results in the formation of pyruvate, which is transported into the mitochondria. Here, the pyruvate is decarboxylated and oxidized to form acetyl-CoA, a reaction catalyzed by the pyruvate dehydrogenase complex. Acetyl-CoA is the correct substrate that enters the Krebs cycle. Other options, such as α-ketoglutaric acid, glyceric acid, and citric acid, are either intermediates or products of different processes within cellular respiration and are not directly formed from pyruvate decarboxylation.