Potentials of concentric charged spherical shells

1. A.
   $\frac{1}{4\pi\epsilon_{0}}\left( \frac{q_{1} + q_{2} + q_{3}}{a} \right),\frac{1}{4\pi\epsilon_{0}}\left( \frac{q_{1} + q_{2} + q_{3}}{\text{ }b} \right),\frac{1}{4\pi\epsilon_{0}}\left( \frac{q_{1} + q_{2} + q_{3}}{c} \right)$
2. B.
   $\frac{1}{4\pi\epsilon_{0}}\left( \frac{q_{1} + q_{2} + q_{3}}{a} \right),\frac{1}{4\pi\epsilon_{0}}\left( \frac{q_{1} + q_{2}}{\text{ }b} + \frac{q_{3}}{c} \right),\frac{1}{4\pi\epsilon_{0}}\left( \frac{q_{1}}{a} + \frac{q_{2}}{\text{ }b} + \frac{q_{3}}{c} \right)$
3. C.
   $\frac{1}{4\pi\epsilon_{0}}\left( \frac{q_{1}}{a} + \frac{q_{2}}{\text{ }b} + \frac{q_{3}}{c} \right),\frac{1}{4\pi\epsilon_{0}}\left( \frac{q_{1} + q_{2}}{\text{ }b} + \frac{q_{3}}{c} \right),\frac{1}{4\pi\epsilon_{0}}\left( \frac{q_{1} + q_{2} + q_{3}}{c} \right)$
4. D.
   $\frac{1}{4\pi\epsilon_{0}}\left( \frac{q_{1}}{a} + \frac{q_{2}}{\text{ }b} + \frac{q_{3}}{c} \right),\frac{1}{4\pi\epsilon_{0}}\left( \frac{q_{1} + q_{2} + q_{3}}{\text{ }b} \right),\frac{1}{4\pi\epsilon_{0}}\left( \frac{q_{1} + q_{2} + q_{3}}{c} \right)$

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