Which of the following compounds does not exhibit paramagnetism?

Which of the following will have two stereoisomeric forms?
$I. [Cr(NO_3)_3(NH_3)_3]$
$II. K_3[Fe(C_2O_4)_3]$
$III. [CoCl_2(en)_2]^+$
$IV. [CoBrCl(ox)_2]^{3-}$

$A$ chemist wants to determine the molecular geometry of the $[CoCl_4]^{2-}$ ion. Which of the following gives the best suggestion for a measurement and for the interpretation of that measurement?

The magnetic moment of a complex ion is $2.83 \ BM$. The complex ion is

For the complex ion $[Ni(Cl)_4]^{2-}$, what is the theoretical value of the magnetic moment (in $BM$)?

What is the magnetic moment value of $Ni^{2+}$ in an aqueous solution in Bohr Magnetons? (Atomic number: $Ni = 28$)