A

Step 1: Let's denote the inner sphere radius as $r_1$ and the outer sphere radius as $r_2$. The capacitance of a spherical capacitor filled with a dielectric is given by the formula:
$$ C = 4\pi\epsilon_0 \frac{r_1 r_2}{r_2 - r_1} \epsilon_r $$
where $\epsilon_r$ is the relative permittivity of the dielectric filling the space between the spheres.

Step 2: We have two halves of the annular space filled with dielectrics of relative permittivities $\epsilon_{r1}$ and $\epsilon_{r2}$. To find the equivalent capacitance of this configuration, we treat each half as a separate capacitor in series.

Step 3: The capacitance of the first half ($C_1$) filled with dielectric $\epsilon_{r1}$ is given by:
$$ C_1 = 4\pi\epsilon_0 \frac{r_1 r_{mid}}{r_{mid} - r_1} \epsilon_{r1} $$
where $r_{mid}$ is the radius of the surface dividing the two dielectrics. For the second half ($C_2$), we have:
$$ C_2 = 4\pi\epsilon_0 \frac{r_{mid} r_2}{r_2 - r_{mid}} \epsilon_{r2} $$

Step 4: Because $C_1$ and $C_2$ are in series, the total capacitance $C_{total}$ can be expressed as:
$$ \frac{1}{C_{total}} = \frac{1}{C_1} + \frac{1}{C_2} $$

Step 5: After some algebraic manipulation and putting $C_1$ and $C_2$ into the formula, we can find that our total capacitance can be represented in terms of an average relative permittivity. By averaging the two dielectrics, we can show:
$$ \epsilon_{r \text{ average}} = \frac{\epsilon_{r1} + \epsilon_{r2}}{2} $$
Step 6: Therefore, in terms of the average, the capacitance is:
$$ C_{total} = 4\pi\epsilon_0 \frac{r_1 r_2}{r_2 - r_1} \epsilon_{r \text{ average}} $$
This demonstrates that the capacitance of the spherical capacitor behaves like it is uniform with an average relative permittivity of $\frac{\epsilon_{r1} + \epsilon_{r2}}{2}$.

Conclusion: Hence, it is shown that the setup with two different dielectrics is effectively equivalent to a single dielectric with the average relative permittivity, $\frac{\epsilon_{r1} + \epsilon_{r2}}{2}$.
Therefore, we conclude that the capacitance will indeed be the same as if the dielectric in the whole annular space has a uniform average relative permittivity.