The $\mathrm{pH}$ at which an amino acid carries no net charge is called its

The isoelectronic point or isoionic point is the pH at which the amino acid does not migrate in an electric field. The net charge on the molecule is affected by the pH of its surrounding environment and can become more positive or negative due to the gain or loss of protons, respectively.

Hence the correct answer is (A) Isoelectric point.