What radioactive source did Geiger and Marsden use in the scattering experiment?

An alpha nucleus of energy $\frac{1}{2}mv^2$ bombards a heavy nuclear target of charge $Ze$. Then the distance of closest approach for the alpha nucleus will be proportional to

An alpha particle colliding with one of the electrons in a gold atom loses

In the Geiger-Marsden experiment,which of the following is used to calculate the trajectory of the $\alpha$-particle?

Statement $(A)$: As one considers orbits with higher values of $n$ in a hydrogen atom,the electric potential energy of the atom increases.
Statement $(B)$: In Thomson's model,an atom is a spherical cloud of positive charges with electrons embedded in it.
Statement $(C)$: The orbital picture in Bohr's model of the hydrogen atom was consistent with the uncertainty principle.

Rutherford's $\alpha$-particle experiment showed that the atoms have