Conformations are different arrangements of atoms that are interconverted by rotation about single bond.
In eclipsed conformation the C-H bond on one carbon is directly aligned with C-H bond on the adjacent carbon.
The angle that separates a bond on one atom from a bond on a adjacent atom is called a dihedral angle.
A staggered conformation with two larger groups `180^@` from each other is called anti. A stagged conformation with two larger group `60^@` from each other is called gauche.
Which of the following is gauche conformer ?

Options

A.
B.
C.
D.