Addition of halogen acid is least in
The regiochemistry of this reaction can be explained through Markovnikov’s Rule. The basics of this rule states that the proton (H+) will add to the less substituted carbon and the halogen (X-) goes to the more substituted carbon .
in the above
D) is more substituted and provide steric hinderence to the proton (H+) addition and hence will be least in Addition of halogen acid .