Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R)
Assertion (A) : Refractive index of glass is higher than that of air.
Reason ( $\mathrm{R}$) : Optical density of a medium is directly proportionate to its mass density which results in a proportionate refractive index.
In the light of the above statements, choose the most appropriate answer from the options given below :

• A

  $(\mathrm{A})$ is not correct but $(\mathrm{R})$ is correct
• B

  Both $(\mathrm{A})$ and $(\mathrm{R})$ are correct and $(\mathrm{R})$ is the correct explanation of (A)
• Correct answer
  C

  $(A)$ is correct but $(\mathrm{R})$ is not correct
• D

  Both (A) and (R) are correct but (R) is not the correct explanation of (A)

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