d
Total charge \(=\sigma \times 4 \pi R^{2}+\sigma \times 4 \pi(2 R)^{2}=20 \mathrm{\sigma \pi R}^{2}\)

\(\frac{\mathrm{Q}_{\mathrm{A}}}{\mathrm{Q}_{\mathrm{B}}}=\frac{1}{2}\)

\(\mathrm{Q}_{\mathrm{A}}=\frac{20}{3} \sigma \pi \mathrm{R}^{2}\) and \(\mathrm{Q}_{\mathrm{B}}=\frac{40}{3} \sigma \pi \mathrm{R}^{2}\)

\(\sigma_{\mathrm{A}}=\frac{\mathrm{Q}_{\mathrm{A}}}{\text { area }}=\frac{20}{3} \frac{\sigma \pi \mathrm{R}^{2}}{4 \pi \mathrm{R}^{2}}=\frac{5 \sigma}{3}\)

\(\sigma_{\mathrm{B}}=\frac{40 \sigma \pi R^{2}}{4 \pi(2 R)^{2}}=\frac{5 \sigma}{6}\)