Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R

Assertion A : In the Ellingham diagram, a sharp change in slope of the line is observed for $\mathrm{Mg} \rightarrow \mathrm{MgO}$ at $\sim 1120^{\circ} \mathrm{C}$

Reason R: There is a large change of entropy associated with the change of state

In the light of the above statements, choose the correct answer from the options given below

1. A Both $\mathbf{A}$ and $\mathbf{R}$ are true and $\mathbf{R}$ is the correct explanation of $\mathbf{A}$ Correct answer
2. B $\mathbf{A}$ is false but $\mathbf{R}$ is true
3. C Both $\mathbf{A}$ and $\mathbf{R}$ are true but $\mathbf{R}$ is NOT the correct explanation of $\mathbf{A}$
4. D $\mathbf{A}$ is true but $\mathbf{R}$ is false