The correct relation between the focal length (f) ​
and radius of curvature (R) of a spherical mirror is:​

The correct option is B R = 2f

The focal length(f) of a spherical mirror is the distance between the principal focus and the pole of the spherical mirror. The principal focus is the point where rays parallel to the principal axis meet after getting reflected from the mirror.
The corret relation between the radius of curvature (R) and the focal length(f) is given by,
R=2f