What is the correct answer?Please explain?(10 points and 5 stars for the best answer)Thanks?

I suppose it's e), the solution contains Ag+ or Pb2+. Just compare the solubility of the compounds and you'll see that the compounds of Ag+ and Pb2+ with the anions from the test tubes are very low soluable. It definitely can't be Na+, K+ or NH4+, because these cations generally form highly soluable compounds.