Which of the following statement (s) is/are true ?
(A) Ag+ ions do not give white precipitate with concentrated HCl
(B) Cu2+ ions produce a white precipitate when KCN solution is added in a small quantity
(C) Hg2+ ions give deep blue precipitate with cobalt acetate and ammonium thiocyanate
(D) Black precipitate of BiI3 turns orange when heated with water