Which of the following elements has the highest work function value?

Given below are two statements: one is labelled as Assertion $(A)$ and the other is labelled as Reason $(R)$. Assertion $(A)$: In aqueous solutions $Cr^{2+}$ is reducing while $Mn^{3+}$ is oxidising in nature.
Reason $(R)$: Extra stability to half-filled electronic configuration is observed than incompletely filled electronic configuration.
In the light of the above statement,choose the most appropriate answer from the options given below:

The electronic configuration of copper $({_{29}}Cu)$ is

Which of the following transition metal ion compounds has a magnetic moment of $4.90 \ BM$?

Which of the following is ferromagnetic?

The spin-only magnetic moment value of the compound with the strongest oxidizing ability among $MnF_{4}$,$MnF_{3}$,and $MnF_{2}$ is $............$ $B.M.$ [nearest integer]