With HBr (no peroxide), which of the following alkenes give a major product that arises from a carbocation rearrangement?

3-Methylbut-1-ene (hydride shift) and 3,3-dimethylbut-1-ene (methyl shift) form secondary cations that become tertiary by a 1,2-shift. 2-Methylbut-2-ene already forms a tertiary cation, and pent-1-ene forms a secondary cation with no better neighbour (a shift would give another secondary cation), so neither rearranges.