Both NADH and FADH₂ are formed during:

Explanation

The Krebs cycle is the stage of cellular respiration where NADH and FADH₂ are produced through the oxidation of acetyl-CoA. In contrast, glycolysis produces only NADH, while the electron transport chain consumes NADH and FADH₂ to generate ATP. Fermentation does not produce FADH₂ and uses NADH to regenerate NAD⁺.