Solution:

Option (iii) is the answer.

Reason:

The correct order of increasing acidic strength is Ethanol < Phenol < Acetic acid < Chloroacetic acid.

Phenol is more acidic than ethanol because in phenol, the phenoxide ion obtained on deprotonation is stabilized by resonance which is not possible in case on ethanol.

Also carboxylic acids are more acidic than alcohols and phenols as the carboxylate ion is stabilized by resonance. Chloroacetic acid is more acidic than acetic acid due to inductive effect of chlorine atom which stabilizes the carboxylate anion.