The first ionisation potential will be maximum for

If $X$ and $Y$ are the second ionisation potentials of alkali and alkaline earth metals of the same period,then:

The ionization energy will be higher when the electron is removed from

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:

Which of the following is the $CORRECT$ decreasing order of ionisation enthalpy for the given elements?

Identify the element which has the highest second ionisation enthalpy.