Below are two statements. One is labeled as Assertion $(A)$ and the other as Reason $(R).$
Assertion $(A):$ When using an aqueous solution of $KOH$ in a volumetric analysis,its concentration should be checked before use.
Reason $(R):$ $KOH$ solution absorbs atmospheric $CO_2$ when it gets old.
In the context of the above statements,choose the correct answer from the options given below:

• A
  $A$ is false,but $R$ is true.
• B
  Both $A$ and $R$ are true,but $R$ is not the correct explanation of $A.$
• C
  Both $A$ and $R$ are true,and $R$ is the correct explanation of $A.$
• D
  $A$ is true,but $R$ is false.