A, to the container and the ball as a whole for the object of study, analyze the force can be known: vertical direction: total gravity, the ground support, horizontal direction of the ground on the hemispherical container without friction. Therefore, A error.
B, C on the ball force analysis: gravity G, spring force F and container support N, as shown in the figure, by the conditions of equilibrium and geometric relationship can be seen, N = F = mg, so B error; C is correct;
D, Hooke's law: the compression of the spring is x =
=
, then the spring has original length R+x=R+
, so D is correct.
So choose CD
.