2,2-Dimethyloxirane is subjected to the following conditions. Select all correct product assignments.

1. A$\mathrm{CH}{}_3\mathrm{ONa}$/$\mathrm{CH}{}_3\mathrm{OH}$, then $\mathrm{H}{}_3\mathrm{O}{}^{+}$ gives 1-methoxy-2-methylpropan-2-ol
2. B$\mathrm{LiAlH}{}_4$, then $\mathrm{H}{}_3\mathrm{O}{}^{+}$ gives 2-methylpropan-2-ol
3. C$\mathrm{CH}{}_3\mathrm{MgBr}$ (excess), then $\mathrm{H}{}_3\mathrm{O}{}^{+}$ gives 2,2-dimethylpropan-1-ol
4. D$\mathrm{CH}{}_3\mathrm{OH}$ with a catalytic amount of $\mathrm{H}{}_2\mathrm{SO}{}_4$ gives 2-methoxy-2-methylpropan-1-ol