Which carrier must be regenerated in its oxidized form for the second half of glycolysis to keep running?

1. Step six loads high-energy electrons onto the oxidized carrier, turning it into NADH. 2. Continuation of that reaction depends on the availability of the oxidized form of the carrier. 3. NADH must therefore be continuously oxidized back so the step can keep going. 4. If the oxidized form is not available, the second half of glycolysis slows down or stops. 5. Coenzyme A carries acetyl groups into a later pathway and cannot substitute here. _Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 7 "Cellular Respiration", section 7.2 Glycolysis_