The dihedral angle in the staggered form of the Newman projection of $1,1,1-$trichloroethane is $60^{\circ}$. (Round off to the nearest integer)

Given below are two statements:
Statement $I$: There are several conformers for $n$-butane. Out of those conformers,the fully eclipsed conformer (dihedral angle $0^{\circ}$) is the least stable and the anti-staggered conformer (dihedral angle $180^{\circ}$) is the most stable.
Statement $II$: As the dihedral angle increases from $0^{\circ}$ to $60^{\circ}$,torsional strain decreases from the fully eclipsed conformer $(X)$ to the gauche conformer $(Y)$.
In the light of the above statements,choose the correct answer from the options given below:

Arrange the following conformational isomers of $n$-butane in order of their increasing potential energy:

With respect to the conformers of ethane,which of the following statements is true?

The most stable conformation for $n$-butane is

On Pluto,where everything is frozen,astronauts discovered two forms of butane: gauche and anti. Assuming that there are no rotations around single bonds,which statement about the two forms is correct?