$A$ brass disc and a carbon disc of same radius are assembled alternatively to make a cylindrical conductor. The resistance of the cylinder is independent of the temperature. The ratio of thickness of the brass disc to that of the carbon disc is [$\alpha$ is temperature coefficient of resistance and neglect linear expansion].

• A
  $\left| \frac{\alpha_C \rho_C}{\alpha_B \rho_B} \right|$
• B
  $\left| \frac{\alpha_C \rho_B}{\alpha_B \rho_C} \right|$
• C
  $\left| \frac{\alpha_B \rho_C}{\alpha_C \rho_B} \right|$
• D
  $\left| \frac{\alpha_B \rho_B}{\alpha_C \rho_C} \right|$