Assertion : Liquefaction of $\mathrm{NH}_3$ is easier than $\mathrm{CO}_2$. Reason : $T_c$ of $\mathrm{CO}_2$ is more than that of $\mathrm{NH}_3$.

• A

  If both assertion and reason are true and reason is the correct explanation of assertion.
• B

  If both assertion and reason are true but reason is not the correct explanation of assertion.
• Correct answer
  C

  If assertion is true but reason is false.
• D

  If both assertion and reason are false.

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