Given below are two statements. One is labelled as
Assertion $\mathrm{A}$ and the other is labelled as Reason $\mathrm{R}$.
Assertion $\mathrm{A}:$ Sharp glass edge becomes smooth on heating it up to its melting point.

Reason $\mathrm{R}:$ The viscosity of glass decreases on melting.

Choose the most appropriate answer from the options given below.

• A

  $\mathrm{A}$ is true but $\mathrm{R}$ is false
• Correct answer
  B

  Both $\mathrm{A}$ and $\mathrm{R}$ are true but $\mathrm{R}$ is NOT the correct
  explanation of $\mathrm{A}.$
• C

  $\mathrm{A}$ is false but $\mathrm{R}$ is true.
• D

  Both $\mathrm{A}$ and $\mathrm{R}$ are true and $\mathrm{R}$ is the correct explanation of $\mathrm{A}$.

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