Question #2fd77

The stuctural formulae of all possible isomers (with their names) having molecular formula ${C}_{5} {H}_{10}$ are written above. Of these isomers first 5 isomers contain $C = C$ (unsaturation). So they all undergo addition reaction with $B {r}_{2}$. Hence they all decolorise red $B {r}_{2}$ water.