The test used for identifying carbon-carbon double bond in an alkene is 

Baeyer test is used for identifying carbon-carbon double bonds in an alkene.

In this test, we use alkaline ${\mathrm{KMnO}}_4$ as a reagent.

During this test, decolourisation of alkaline ${\mathrm{KMnO}}_4$ confirms the presence of carbon-carbon double bonds.

Hence, option (A) is correct.