$\,\begin{array}{*{20}{c}}
{\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,COOH}\\
{\,\,\,\,\,\,\,\,\,|}\\
{\mathop {N{H_3}}\limits^{\,\, \oplus } - C - H}\\
{\,\,\,\,\,\,\,\,\,\,|}\\
{\,\,\,\,\,\,\,\,\,\,R}
\end{array}\,\,\,$
(a) Water solubility is maximum at a $pH$ when concentrations of anions and cations are equal
(b) They give ninhydrin test
(c) On reacting with nitrous acid give off ${N_2}$
$(i)$ Diastereomers $(ii)$ Geometrical isomers
$(iii)$ Epimers $(iv)$ Anomers
$(v)$ Enantiomers