Which of the following carbocations can be converted into a more stable carbocation by a single 1,2-shift of H or $\mathrm{CH}{}_3$?

Option 1: hydride shift gives the tertiary cation. Option 2: methyl shift gives the tertiary cation $(\mathrm{CH}{}_3){}_2\mathrm{C}{}^{+}-\mathrm{CH}(\mathrm{CH}{}_3){}_2$. Option 3 is already tertiary, and in option 4 any shift would give a non-benzylic secondary cation, which is less stable than the benzylic one.