Answer:
Its focal length is positive
Step-by-step explanation:
A concave mirror is shown in attached figure. The distance from the pole to the focus of the mirror is called its focal length. Spherical mirrors are a part of a sphere.
As per conventions, we know that the axis opposite to x axis is taken as negative.
So, it is clear that the focal length of spherical concave mirror is negative.
Hence, the incorrect option is (c) " its focal length is positive".