Looking along the C2-C3 bond of butane in a staggered conformation, the two methyl groups are $6 0^{\circ}$ apart. This conformation is called:

Answer: D

In a staggered conformation the groups on adjacent carbons are separated by

6 0^{\circ}

(gauche) or

18 0^{\circ}

(anti). A dihedral angle of

6 0^{\circ}

between the two methyl groups is the gauche conformation of butane. Eclipsed conformations have dihedral angles of

0^{\circ}

12 0^{\circ}