According to the New Cartesian Sign Convention, for a spherical mirror, distances measured against the direction of incident light are taken as:
Correct: B
In the New Cartesian Sign Convention, the pole (or optical center for lenses) is taken as the origin. The incident light is generally considered to travel from left to right. Distances measured in the same direction as incident light are taken as positive, while distances measured against the direction of incident light are taken as negative.