The peroxide effect involves:
(A) Ionic mechanism
(B) Free radical mechanism
(C) Heterocyclic fission of double bond
(D) Homolytic fission of double bond

Hint: Peroxide effect is also called as Anti-Markovnikov’s rule.
Markovnikov’s rule: In this reaction, there is an involvement of Hydro halides to unsaturated compounds. The hydrogen from hydro halides is going to attach to carbon where high numbers of hydrogens are present. In Anti- Markovnikov's rule: The hydrogen from hydro halides is going to attach to carbon where fewer numbers of hydrogens are present.

Complete step by step solution:
-In Markovnikov’s rule the addition of hydro halide is through an ionic mechanism. Means there is an involvement of cations and anions in the reaction.
-Coming to Anti-Markovnikov's rule or peroxide effect the addition of hydro halides is not through the ionic mechanism. It is through a mechanism where free radicals are going to involve.
-The representation of the peroxide effect or Anti-Markovnikov’s rule is as follows.

-Because of the initiation of the reaction through free radicals the addition of hydro halides to the position is going to change in alkenes.
- That is why the above reaction is called Anti-Markovnikov's rule or peroxide effect.
-Therefore a free radical mechanism is involved in the peroxide effect.

So, the correct option is B.

Note: The original mechanism of the Markovniov’s rule is going to change because of the presence of the peroxide chemical at the initial stage of the reaction of hydro halides with alkenes. That is why the reaction is called peroxide effect.