A Charge Q Is Spread Uniformly Along the Circumference of a Circle

A charge Q is spread uniformly along the circumference of a circle of radius R.A point particle with charge q is placed at the center of this circle.The total force exerted on the particle q can be calculated by Coulomb's law:

A) if you use R for the distance
B) if you use 2R for the distance
C) if you use 2 $\pi$ R for the distance
D) and the result of the calculation is zero
E) none of the above