In a set of nine experiments used to compare the reactivity of the halogens, an aqueous solution of each halogen was mixed with an equal volume of an aqueous solution containing halide ions, as set out in the table below. The nine mixtures were then shaken with hexane. After that, the nine tubes were corked and left standing so that the aqueous and organic solvents could separate into layers. In how many test-tubes did a purple upper layer appear?
- A1
- B2
- C3
- D5