Insoluble sulfide compounds are generally black in color. Which of the following combinations could yield a black precipitate? a) Na2S(aq) + KCl(aq) b) Li2S(aq) + Pb(N03)2(aq) c) Pb(C103)2(aq) + NaNO3(aq) d) AgNo3(aq) + KCl(aq) e) K2S(aq) + Sn(N03)4(aq)