Consider a uniform spherical charge distribution of radius $R_1$ centred at the origin $O$. In this distribution,a spherical cavity of radius $R_2$,centred at $P$ with distance $OP = a = R_1 - R_2$ (see figure) is made. If the electric field inside the cavity at position $\vec{r}$ is $\vec{E}(\vec{r})$,then the correct statement$(s)$ is(are):

• A
  $\vec{E}$ is uniform,its magnitude is independent of $R_2$ but its direction depends on $\vec{r}$
• B
  $\vec{E}$ is uniform,its magnitude depends on $R_2$ and its direction depends on $\vec{r}$
• C
  $\vec{E}$ is uniform,its magnitude is independent of $a$ but its direction depends on $\vec{a}$
• D
  $\vec{E}$ is uniform and both its magnitude and direction depend on $\vec{a}$