Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A$: $LiF$ is sparingly soluble in water.
Reason $R$: The ionic radius of $Li^{+}$ ion is smallest among its group members,hence it has the least hydration enthalpy.
In the light of the above statements,choose the most appropriate answer from the options given below.

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