The glycolytic pathway must be supplied with its primary oxidizing agent .

The answer is NAD+.

NAD+ is the primary oxidizing agent in the glycolytic pathway. Oxidizing agents gain electrons and thus, they are reduced in a reaction. In the glycolytic pathway, NAD+ server the oxidizing agent. It accepts electrons from the molecules, such as some intermediates of the glycolytic pathway. As the result, it is reduced to NADH which can serve in some reactions as a reducing agent.