Which transformation could take place at the anode of an electrochemical cell?

As I found out the choices for your question which are:

A) F2 to F-

B) Cr2O7² - → Cr2+

C) O2 to H2O

D) HAsO2 to As

Unfortunately, the answer does not belong to the choices provided. In fact, it is the oxidation half-reaction that occurs at the anode of an electrode for it to transform chemical energy to consumable electrical energy.