| $pH$ at Isoelectric point | |
| $(Amino acid)_I$ | $6$ |
| $(Amino acid)_{II}$ | $9.8$ |
| $(Amino acid)_{III}$ | $3.9$ |
$(Amino acid)_{II}$ is ____ ?
(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 ${N_2}$