Neopentyl bromide gives a carbocation as an intermediate which undergoes for rearrangement and shows a E₁ mechanism (even has no β-H atom).

Thus rearrangement of carbocations by E₁ mechanism is the correct option.

Reactions happening under E₁ mechanism will yield rearranged products due to shift of atoms or groups leading to more stable carbocations. Neopentyl bromide in a solvent ethanol or formic acid (ionizing solvent) undergoes E₁ reaction producing

(CH₃)₂C = CHCH₃

The Mechanism is

Wherever possible, rearrangements happen due to higher stability of secondary or tertiary carbocations. Methyl shift takes place in this example.