A student combined 1 mL of 1.0 M solutions of nitrate salts of barium, calcium, magnesium, and strontium with several different testing reagents. The observations are recorded in this table .
Note: ppt = precipitate, rxn = reaction
An unknown solution contains two of these four ions: barium, calcium, magnesium, and stronium. The unknown solution forms a white precipitate with H2SO4 and it does not react with K2CrO4. What conclusion about the two ions in the unknown can be drawn from this evidence?
(A) It contains only strontium and barium ions.
(B) It contains only barium and calcium ions
(C) It contains barium ion and either magnesium or calcium ions.
(D) It contains strontium ion and either magnesium or calcium ions.