Two rectangular blocks, having identical dimensions, can be arranged either in configuration $\text{I}$ or in configuration $\text{I}\text{I}$ as shown in the figure. One of the blocks has thermal conductivity $\text{K}$ and the other $\text{2 K}$. The temperature difference between the ends along the x-axis is the same in both the configurations. It takes $\text{9 s}$ to transport a certain amount of heat from the hot end to cold end in the configuration $\text{I}$. The time to transport the same amount of heat in the configuration $\text{II}$ is

• Correct answer
  A

  $\text{2.0 s}$
• B

  $\text{3.0 s}$
• C

  $\text{4.5 s}$
• D

  $\text{6.0 s}$

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