Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R.$
Assertion $A :$ Metallic character decreases and non-metallic character increases on moving from left to right in a period.
Reason $R :$ It is due to increase in ionisation enthalpy and decrease in electron gain enthalpy,when one moves from left to right in a period.
In the light of the above statements,choose the most appropriate answer from the options given below :

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