Batch fermentation of glucose to ethanol yields a productivity of 4.5 g^-1L h^-1. If the yeast cell concentration in the fermentation broth is 5% (v/v) and the intracellular NAD⁺/NADH concentration in the yeast cells is 10 μM, the cycling rate of NAD⁺ ⇌ NADH will be

A. 50,000 cycles h^-1

B. 20,000 cycles h^-1

C. 100 cycles h^-1

D. None of the above

Answer: Option B