Two metal rods $1$ and $2$ of same lengths have same temperature difference between their ends. Their thermal conductivities are $K_1$ and $K_2$ and cross sectional areas $A_1$ and $A_2$ , respectively. If the rate of heat conduction in $1$ is four times that in $2$, then

  • A

    $k_1\,\,A_2=4k_2\,\,A_1$

  • B

    $k_1\,\,A_1=4k_2\,\,A_2$

  • C

    $k_1=4k_2$

  • D

    $k_1\,\,A_1^2=4k_2\,\,A_2^2$

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