$\begin{array}{1 1}(a)\;\text{The pH at which [Anion] > [Cation] is called isoelectric point}\\(b)\;\text{The pH at which [Anion] = [Cation] is called isoelectric point}\\(c)\;\text{The pH at which [Anion] < [Cation] is called isoelectric point}\\(d)\;\text{when solution has one type of ions}\end{array} $