(A) : For ${\mathrm{C}}_2{\mathrm{H}}_6$ staggered conformation is more stable than eclipsed

(R) : In staggered conformation, the bonded electrons have minimum repulsions

The first staggered structure is and other is Eclipsed.

Staggered conformation - arrangement of carbon and hydrogen at the maximum distance that needed a torsion angle 60⁰.  

Eclipsed conformation - arrangement of carbon and hydrogen at the minimum distance that requires torsion angle 0 ^O.

A compound has higher potential energy those have less torsion angle and a compound are less stable that has higher potential energy.