下列电极反应中,若将离子浓度减少一半,而其它条件不变,则电极电势增大的是 ( )A ClO4- +2H+ +2e = ClO3- +H2OB Co3+ +e = Co2+C S2O82-+2e = 2SO42-D 2Hg2+ +2e = Hg22+请说明过程,谢谢啊!