题目

A man named David went fishing on a holiday．Fishing was his favorite sport，and he had many prizes for fish he had caught． This summer the weather was beautiful and it was very good for fishing，so he decided to travel around the country，and spent a few days fishing in each of the rivers． Unluckily, he didn't have much luck，and he caught only a few small fish．He was quite disappointed and was going to go back home when he heard of a large river that was full of fish nearby．    He found the river quite easily and followed it through the country to a place where it flowed thr用惰性电极电解2 L 1.0 mol/L CuSO4溶液，在电路中通过0.5 mol电子后，调换正负极继续电解，电路中通过了1 mol电子，此时溶液中c(H+)为(假设体积不变)  (　　)A.1.5 mol/LB.0.75 mol/LC.0.5 mol/LD.0.25 mol/L