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

In the different conformations of ethane (staggered, eclipsed, etc.), the molecule rotates around the $C-C$ sigma bond. This rotation changes the dihedral angle (torsional angle) between the $C-H$ bonds on adjacent carbons, but the actual bond lengths ($C-C$ and $C-H$) and the bond angles ($\angle H-C-H$ and $\angle C-C-H$) remain constant.