
The capacitance of parallel plate capacitor with dielectric is $C^{\prime}=\frac{A k \epsilon_{0}}{d}=k C=2 C$
Here $1$ and $2$ plate and $3$ and $4$ plate will make the capacitor of same capacitance $C$ and $2$ and $3$ will make the capacitance of $C^{\prime}$
Here the capacitance in between $1$ and $3$ is $C_{1}=\frac{C C^{\prime}}{C+C^{\prime}}=\frac{C .2 C}{C+2 C}=2 C / 3$
and the capacitance in between $2$ and $4$ is $C_{2}=\frac{C C^{\prime}}{C+C^{\prime}}=\frac{C .2 C}{C+2 C}=2 C / 3$
$\therefore \frac{C_{1}}{C_{2}}=1$
Reason: An electron has a negative charge.

