Which aqueous solution has the highest $pH?0\mathrm{.}1MC{H}_3\frac{C}{O}OH,p{K}_a=4\mathrm{.}70\mathrm{.}1MCuC{l}_2,p{K}_a=7\mathrm{.}50\mathrm{.}1M{H}_3{C}_6{H}_5{O}_7.pK{K}_a=3\mathrm{.}10\mathrm{.}1MZC{l}_2,P{K}_a=9\mathrm{.}0$ pure water