Identify the relationship among the following compounds.

Which of the following pair of compounds are homologous :-

What is the correct relationship in the following compounds ?

${\mathrm{BrCH}}_2-{\mathrm{CH}}_2-\mathrm{CH}=\mathrm{O}$ and ${\mathrm{CH}}_3-{\mathrm{CH}}_2-\underset{\stackrel{|}{\mathrm{Br}}}{\mathrm{C}}=\mathrm{O}$ 

The degree of unsaturation in the following compound is

How many positional isomers are possible for dimethylcyclohexane?

How many aromatic isomers are possible for trichlorobenzene $\left({\mathrm{C}}_6{\mathrm{H}}_3{\mathrm{Cl}}_3\right)$?