The first four ionisation energy values of an element are $191$,$578$,$872$ and $5962 \ kcal$. The number of valence electrons in the element is :-

Assertion $(A)$: The first ionisation energy of $Be$ is greater than that of $B$.
Reason $(R)$: $2p$ orbital has lower energy than $2s$ orbital.

Which of the following species has the lowest ionization potential?

Assertion $(A)$: Boron has a smaller first ionisation enthalpy than beryllium.
Reason $(R)$: The penetration of a $2s$-electron to the nucleus is more than the $2p$-electron; hence,the $2p$-electron is more shielded by the inner core of electrons than $2s$-electrons.

How would you explain the fact that the first ionization enthalpy of sodium is lower than that of magnesium but its second ionization enthalpy is higher than that of magnesium?

Given below are two statements:
Statement $I$: The first ionization energy of $Pb$ is greater than that of $Sn$.
Statement $II$: The first ionization energy of $Ge$ is greater than that of $Si$.
In the light of the above statements,choose the correct answer from the options given below: