A, B and C are spherical Gaussian surfaces as shown in figure. Then 

According to Gauss’ law, ${\mathrm{\varphi }}_{\mathrm{E}}=\frac{{\mathrm{Q}}_{\mathrm{net}}}{{\epsilon }_0}\Rightarrow {\mathrm{\varphi }}_{\mathrm{E}}\propto {\mathrm{Q}}_{\mathrm{net}}$

$$\begin{gathered} \mathrm{For}\mathrm{A}, {\mathrm{Q}}_{\mathrm{net}}\propto +8\mathrm{\mu C}, \\ \mathrm{for}\mathrm{B}, {\mathrm{Q}}_{\mathrm{net}}\propto +9\mathrm{\mu C}, \\ \mathrm{for}\mathrm{C}, {\mathrm{Q}}_{\mathrm{net}}\propto +3\mathrm{\mu C} \end{gathered}$$