An inorganic substance gives balck ppt in group II which is dissolve in aqua regain Evapotate off aqus regain and dilute it with water .To this few drop of ammonium thiocyanate and sodium acelete followed by `Co(NO_(3))_(2)` are added .A deep blue colour or ppt .is obtained .This is due to presence of
A. `Hg^(2+)`
B. `Bi^(3+)`
C. `Pb^(2+)`
D. `Cd^(2+)`