Assertion (A) Finely divided charcoal can act as an adsorbent. Reason (R) Finely divided material has small surface area.

• A

  Both $A$ and $R$ are correct and $R$ is the correct explanation of $A$.
• B

  Both $\mathrm{A}$ and $\mathrm{R}$ are correct and $\mathrm{R}$ is not the correct explanation of $\mathrm{A}$.
• Correct answer
  C

  $A$ is correct but $R$ is incorrect.
• D

  $A$ is incorrect but $\mathrm{R}$ is correct.

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