(A) : The electric field due to a discrete charge configuration is not defined at the locations of the discrete charges
(R) : For a surface charge distribution, electric field is discontinuous across the surface.

The electric field due to a discrete charge configuration is not defined at the locations of the discrete charges. 

$\mathrm{E}=\frac{\mathrm{kQ}}{{\mathrm{r}}^2}=\frac{\mathrm{kQ}}{0}=\mathrm{Not} \mathrm{define}$

For a surface charge distribution, electric field is discontinuous across the surface. Inside the surface of conducting sphere the field is zero and outside it is perpendicular to the surface.