The generation of carbocations with the present three alcohol substrates in terms of the reaction mechanism is as follows:.

Here 1° carbocation formation occurs through protonation of 1° -OH followed by a nucleophilic attack.

Here $2° carbocation\; formation$occurs which is comparatively more stable than primary alcohol.

the rate of S_N1 mechanism will increase as stability of carbocation will increase

Similarly, the tertiary carbocation formed from tertiary alcohol is most stable so therefore here the rate of reaction by S_N1 mechanism is highest.

So, the correct option is second

Conclusion:- Higher the stability of carbocation intermediate higher will be the rate of halogenation of given alcoholic substrates by haloacids.