Which one of the following reagents is used for the detection of unsaturation in alkenes?

Cold dilute alkaline ${\mathrm{KMnO}}_4$ is called as baeyers reagent which is a strong oxidizing agent that is utilized for qualitative analysis to check unsaturation this checks unsaturation between carbon- carbon double bond.

In this test, the pink color potassium permanganate disappears when alkaline potassium permanganate is added to an unsaturated hydrocarbon. The disappearance of pink color may take place with or without the formation of a brown precipitate of manganese oxide.