Combining gravity and tension, the resultant force points to the center of the circle, which is obtained from the geometric relationship. The resultant force is f = mg tan θ ①;

According to the centripetal force formula, f = mω 2r ②;

Let the height difference between the rope and the suspension point be h, and we can get from the geometric relationship: r = htanθ ③;

From ① ② ③, ω=gh, which has nothing to do with the length and rotation radius of the rope;

And by T = 2ωω, so the period has nothing to do with the length of the rope and the radius of rotation, so a is correct;

From v=wr, it can be seen that the rotation radii of the two balls are different, so the linear velocity is different, so B is wrong;

Rope tension: T=mgcosθ, so the rope tension is different, so C is wrong;

From F=ma=mω2r, it can be seen that the rotation radii of the two balls are different, so the centripetal force is different, so D is wrong;

So choose a.