The dihedral angle between the two methyl groups of n-butane (about $\mathrm{C}{}_2-\mathrm{C}{}_3$) is changed from $180^{\circ }$ to $0^{\circ }$ in steps, passing through $120^{\circ }$ and $60^{\circ }$. The correct sequence of energy extrema encountered is

1. Aminimum (anti), minimum (gauche), maximum (CH3 eclipsed with H), maximum (CH3 eclipsed with CH3)
2. Bmaximum (anti), minimum (CH3 eclipsed with H), maximum (gauche), minimum (CH3 eclipsed with CH3)
3. Cminimum (anti), maximum (gauche), minimum (CH3 eclipsed with H), maximum (CH3 eclipsed with CH3)
4. Dminimum (anti), maximum (CH3 eclipsed with H), minimum (gauche), maximum (CH3 eclipsed with CH3)