A(predominantly ) is

The correct answer is (4).

The reaction of 3-methylbutan-2-ol with HBr will give 2-Bromo-2-methylbutane.

Mechanism :

Step 1: In the first step, the −OH group is protonated.

Step 2: In the second step, a molecule of water is lost to form a secondary carbocation.

Step 3: Third step is the rearrangement of less stable secondary carbocation to more stable tertiary carbocation through 1,2-hydride shift.

Step 4: Final step is the nucleophilic attack of bromide ion on tertiary carbocation to form 2-bromo-2-methylbutane.