複選題15. There are two groups of solutions: group A includes the water solutions of 0.01M AgNO₃, 0.01M Pb(NO₃)₂, 0.01M Ba(NO₃)₂, and 0.01M Ni(NO₃)₂. Group B includes the water solution of 0.01M NaCl, 0.01M Na₂SO₄, and 0.01M Na₂S. If we take each solution in group A to mix with equal volume of each solution in group B, which of the following statements is correct ? (A) There are 8 solutions with precipitation (B) there are 5 solutions with no precipitation (C) there are 4 solutions with black precipitation (D) there are 5 solutions with white precipitation (E) none of the mixtures with Ni(NO₃)₂ has the precipitation