**Core Concept**
The redox potential is a measure of the tendency of a molecule to gain or lose electrons and is crucial in understanding the electron transport chain and cellular respiration. It is expressed in millivolts (mV) and is influenced by the standard reduction potential of the molecule.

**Why the Correct Answer is Right**
The correct answer, FADH2, has a higher redox potential compared to NADH because it is reduced at a lower potential. FADH2 is reduced to FAD by the breakdown of acetyl-CoA in the citric acid cycle, whereas NADH is reduced to NAD+ by the breakdown of glucose in glycolysis. This difference in redox potential affects the electrons' flow through the electron transport chain, ultimately influencing the efficiency of ATP production. The higher redox potential of FADH2 allows it to donate its electrons at a higher energy level, resulting in a greater ATP yield.

**Why Each Wrong Option is Incorrect**
**Option A:** NADH has a lower redox potential compared to FADH2 and is involved in the initial stages of cellular respiration.
**Option B:** The redox potential of coenzyme Q (CoQ) is not as high as FADH2 and is involved in the electron transport chain but not as a direct electron donor.
**Option C:** The redox potential of cytochrome c is not as high as FADH2 and is involved in the electron transport chain as a carrier of electrons.

**Clinical Pearl / High-Yield Fact**
The electron transport chain is a critical process in cellular respiration, and understanding the redox potentials of key molecules like FADH2 and NADH is essential for grasping how cells generate energy.

**Correct Answer:** C. FADH2