Which of the $Na^+$ and $He$ has completely filled $K$ and $L$ shells? Give a reason to support your answer.

(A) $Na^+$ has completely filled $K$ and $L$ shells.
$Na$ atom has an atomic number of $11$,with an electronic configuration of $(2, 8, 1)$.
When $Na$ loses one electron from its outermost $M$ shell to form $Na^+$,its electronic configuration becomes $(2, 8)$.
Here,the $K$ shell contains $2$ electrons and the $L$ shell contains $8$ electrons,both of which are completely filled.
In contrast,$He$ (atomic number $2$) has only the $K$ shell,which contains $2$ electrons,and it does not possess an $L$ shell.