Two electrons occupying the same orbital are distinguished by

Correct statements for an element with atomic number $9$ are:
$A.$ There can be $5$ electrons for which $m_{s}=+\frac{1}{2}$ and $4$ electrons for which $m_{s}=-\frac{1}{2}$
$B.$ There is only one electron in $p_z$ orbital
$C.$ The last electron goes to an orbital with $n=2$ and $l=1$
$D.$ The sum of angular nodes of all the atomic orbitals is $1$
Choose the correct answer from the options given below:

The electronic configuration of fluorine is

Identify the pair of orbitals having similar $(n + l)$ values from the following.

After the $np$ orbital is completely filled,in which orbital does the next electron enter?

Write about the magnetic quantum number $(m_{l})$.