Arrange the following compounds in the increasing order of their densities.

(a) (i) < (ii) < (iii) <(iv) (b) (i) < (iii) < (iv) < (ii)

(c) (iv) <(iii) <(ii) < (i) (d) (ii) < (iv) < (iii) < (i)

Density is directly related to molecular mass. Higher the molecular mass, higher will be the density of the compound. Among the four given compounds, the order of molecular mase is

benzene < chlorobenzene < dichlorobenzene < bromochlorobenzene

Therefore, the increasing order of their densities is the same as above.

Hence, option (a) is correct.