The distance between two plates of a capacitor is $d$ and its capacitance is $C_1$, when air is the medium between the plates. If a metal sheet of thickness $\frac{2d}{3}$ and of the same area as plate is introduced between the plates, the capacitance of the capacitor becomes $C_2$ . The ratio $\frac{C_2}{C_1}$ is

• Correct answer
  A

  $3 : 1$
• B

  $2 : 1$
• C

  $4 : 1$
• D

  $1 : 1$

Hence, the correct answer is option: 'A'.