Which of the following hydrocarbons is the most reactive towards addition of $\mathrm{H}_2 \mathrm{SO}_4$ ?

As $\pi$-bond is more activated, the addition of $\mathrm{H}_2 \mathrm{SO}_4$ is carried out fastly. In the given compound, 3-methyl but-1-ene. Undergoes rapid addition, because $\pi$-bond is activated by hyperconjugation and after addition the most stable $3^{\circ}$-carbocation is formed.