Given below are two statements: one is labelled as Assertion \(A\) and the other is labelled as Reason \(R\) : Assertion \(A:\) The first ionisation enthalpy decreases across a period. Reason \(R:\) The increasing nuclear charge outweighs the shielding across the period. In the light of the above statements, choose the most appropriate from the options given below:

1. A Both \(\mathrm{A}\) and \(\mathrm{R}\) are true and \(\mathrm{R}\) is the correct explanation of \(A\)
2. B \(A\) is true but \(R\) is false
3. C \(A\) is false but \(R\) is true
4. D Both \(\mathrm{A}\) and \(\mathrm{R}\) are true but \(\mathrm{R}\) is \(NOT\) the correct explanation of \(\mathrm{A}\)