Which of the following carbocations will rearrange (by a 1,2-hydride or 1,2-methyl shift) to a more stable carbocation?

$\mathrm{CH}{}_3\mathrm{CH}{}_2\mathrm{CH}{}_2{}^{+}$ (primary) gives the secondary isopropyl cation by H shift. $(\mathrm{CH}{}_3){}_2\mathrm{CHCH}{}_2{}^{+}$ gives the tertiary tert-butyl cation by H shift. Neopentyl $(\mathrm{CH}{}_3){}_3\mathrm{CCH}{}_2{}^{+}$ gives the tertiary tert-pentyl cation by methyl shift. The tert-butyl cation is already tertiary and does not rearrange.