Which of the following is air pollutant?

$$ \text { Hybridisations of carbon-2 in } P \text { and } Q \text { are respectively. } $$

A benzene derivative did not produce white precipitate with the ammonical silver nitrate solution but decolorised the cold dilute alkaline $\mathrm{KMnO}_4$ solution. The compound is

Which of the following can be used as the test for unsaturation with regard to colour change of reaction?