27) Why does the oxidation number decrease in a reduction reaction? a. gaining electrons b. losing electrons c. addition of OHions d. addition of H3O+ions 28) In the half-reaction: Ag++eAg, why do silver ions change into silver atoms? a. silver ions ionized b. silver ions are oxidized c. silver ions are reduced d. the oxidation number of silver ions does not change 29) In an oxidation-reduction reaction, CO turns into CO2, how many electrons are lost or gained from C ? a. lose one electron b. lose two electrons c. gain one electron d. gain two electrons