Answer:
Option D is the answer :
Analytical Groups II and III
Explanation:
Group II (Cu2+, Bi3+, Cd2+, Hg2+, As3+, Sb3+, Sn4+) cations produce very insoluble sulfides
(Ksp values less than 10-30) so they can be precipitated by low amounts of sulfide ion; this can be
achieved by adding an acidic solution of H2S.
Group III (Al3+, Cr3+, Fe3+, Zn2+, Ni2+, Co2+, Mn2+) cations produce slightly soluble sulfides
(Ksp values more than 10-20) so they can be precipitated by relatively high amounts of sulfide ion;
this can be achieved by adding a basic solution of H2S