Question

What does the radius of a sphere join?

any two points on the sphere and does not contain the center

any two points on the sphere and contains the center <~my choice

any two points on the sphere

the center and a point on the sphere

Answer 1

I think you'd better consider a circle. What does a radius of a circle join?

Care to revise your answer?

Answer 2

The center and a point on the sphere.