Given below are two statements $:$ one is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A :$ Work done in moving a test charge between two points inside a uniformly charged spherical shell is zero,no matter which path is chosen.
Reason $R :$ Electrostatic potential inside a uniformly charged spherical shell is constant and is same as that on the surface of the shell.
In the light of the above statements,choose the correct answer from the options given below.

• A
  $A$ is true but $R$ is false
• B
  Both $A$ and $R$ are true and $R$ is the correct explanation of $A$
• C
  $A$ is false but $R$ is true
• D
  Both $A$ and $R$ are true but $R$ is $\text{NOT}$ the correct explanation of $A$