Answer:
Cell potential is defined as D. difference between reduction potentials of half cells.
Step-by-step explanation:
The cell potential is calculated by taking the difference in the half reaction which is reductive and the half reaction which is oxidative.
Symbolically: E°cell = E°cathode − E°anode
Under standard temperature and pressure condition, the standard cell potential of hydrogen electrode is 0 V. The cell potential is obtained by subtracting because it is impossible to measure the exact single electrode potential hence it is measured in the form of difference.