The first statement "Consider a favorable reduction-oxidation (redox) reaction: the reactant that is reduced will have a less positive reduction potential."
The reduction potential is the tendency of a molecule to gain electrons and get reducted. Larger positive values of reduction potential (measures in millivolts) indicate a greater tendency of the molecule to get reduced, and the smaller the value of reduction potential, the less likely it is for the molecule to get reducted.
For the redox reaction, the reactant that is reduced will have a less positive potential reduction, this happens because the molecule is already reduced, so the statement is TRUE.
Second statement "Phosphocreatine is an energy storage molecule that can be used to regenerate NAD+ for muscle contraction."
Phosphocreatine is a substance found in the muscle tissue of vertebrates. Its function is to maintain the pH of the environment within the muscle fiber and recycle ADP into ATP for muscular activity. The reaction in which the Phosphocreatine gives a Phosphate to ADP to create ATP is possible thanks to the action of the enzyme Creatin Kinase as follows:
The second statement is therefore FALSE since the Phosphocreatine is used to recycle ATP and not NAD+