The most acidic compound among the following is:
 

1.  Benzyl alcohol                   

2.  Cyclohexanol

3.  Phenol                               

4.  m-Chlorophenol

Hint: Phenol is more acidic than alkyl alcohol

The alpha carbon of benzyl alcohol and cyclohexanol is sp3 hybridised while in phenol and m-chlorophenol, it is sp2 hybridised. In m-chlorophenol electron withdrawing group(-Cl) is present at the meta position.

The presence of electron electron-withdrawing group increases the acidic strength. So, m-chlorophenol is the most acidic among all the given compounds.

The acidity order is as follows:

m-chlorophenol > Phenol >  Benzyl alcohol  >  Cyclohexanol

The correct option is the fourth option