During chlorination process, aqueous (aq) chlorine reacts rapidly with water to form $Cl^-,HOCl$, and $H^+$ as shown below $$Cl_2(aq)+H_2O\:{\large\rightleftharpoons}\:HOCl+Cl^-+H^+$$ The most active disinfectant in the chlorination process from amongst the following, is
1. $H^+$
2. $HOCl$
3. $Cl^-$
4. $H_2O$