We can distinguish by bromine test is:(A) Alkenes(B) Alkynes(C) Alkanes(D) Both A and B

The bromine test is commonly used to distinguish between alkenes and alkynes. Alkenes and alkynes are both unsaturated hydrocarbons, meaning they contain double or triple bonds, respectively.

When a bromine solution is added to an alkene or alkyne, a reaction takes place in which the bromine molecule (Br2) adds across the double or triple bond, resulting in the decolorization of the bromine solution. This reaction occurs because the pi bonds in the unsaturated hydrocarbons are more reactive than the sigma bonds in the saturated hydrocarbons (such as alkanes).

On the other hand, alkanes do not react with bromine under normal conditions. Alkanes are saturated hydrocarbons that only contain single bonds, and the C-C sigma bonds in alkanes are relatively stable and unreactive towards bromine.

Therefore, the correct answer is (D) Both A and B, as the bromine test can be used to distinguish both alkenes and alkynes from alkanes.