Which of the Following is NOT a Redox Pair

Question

Which of the following is NOT a redox pair? A) fumarate/succinate B) NADH + H⁺/NAD C) H2S/H2O D) quinone/quinol (Q/QH2) E) FAD/FADH2

Accepted Answer

H₂S/H₂O is not a redox pair because they do not directly interconvert through a redox reaction. The other pairs involve direct electron transfer between the two species.