The center of a sphere is
-a line segment from the center point to the surface of the sphere.
-a fixed point equidistant from all points on the surface of the sphere.
-a three-dimensional circle in which all points are equidistant from a fixed point.
-the same as the base of the sphere.

Option B is correct.

Step-by-step explanation:

Center of the Sphere is a fixed point in its interior which is equidistant from each point on sphere.

Option A is not right because it says center is line segment.

Option B is right as it says it is fixed and equidistant from point of surface.

Option C is not right because it says its a three dimensional Circle.

Option D is not right because it says it is on surface but center is in interior.

Therefore, Option B is correct.