For the ionisation $\mathrm{R}-\mathrm{X}\to \mathrm{R}{}^{+}+\mathrm{X}{}^{-}$ (rate-determining step of ${\mathrm{S}}_{\mathrm{N}}1$), which conclusions from the Hammond postulate are correct?

1. AThe transition state resembles the carbocation (ion pair) more than it resembles $\mathrm{R}-\mathrm{X}$.
2. BFactors that stabilise the carbocation also lower the energy of the transition state, though by a smaller amount.
3. C$(\mathrm{CH}{}_3){}_3\mathrm{C}-\mathrm{Cl}$ ionises faster than $(\mathrm{CH}{}_3){}_2\mathrm{CH}-\mathrm{Cl}$ under identical conditions.
4. DThe transition state resembles $\mathrm{R}-\mathrm{X}$, so carbocation stability does not affect the rate.