Concept:Bromine water is used to test for unsaturation.It is decolorized by alkenes and alkynes, but not by alkanes.Explanation:Hydrocarbon X decolorized bromine water, so X is unsaturated. Hydrocarbon Y did not decolorize bromine water, meaning Y is saturated. Alkanes are saturated hydrocarbons and do not react with bromine water. Therefore, Y belongs to the alkane family.Answer:D. Alkanes