In nine separate experiments, a halogen reactivity test is carried out by adding an aqueous solution of each halogen to the same volume of an aqueous solution that contains halide ions, as shown in the table. Each of the nine mixtures is then shaken on its own with the same volume of hexane. The tubes are then allowed to stand so that the aqueous layer and the organic layer form separate layers. How many test-tubes have a purple upper hexane layer?
- A1
- B2
- C3
- D5