What is the value of effective magnetic moment found in $+3$ oxidation state of Chromium $(Z=24)$ (in $BM$)?

For which pair is the magnetic moment $\mu = \sqrt{15} \ BM$ correct?

What are the complex ions $[Co(NH_3)_5(NO_2)]^{2+}$ and $[Co(NH_3)_5(ONO)]^{2+}$ called?

Select the correct statement about $[Mn(CO)_4NO]$ which is diamagnetic.

Which of the following compounds shows optical isomerism?

The correct statement on the isomerism associated with the following complex ions,
$A$. $[Ni(H_2O)_5NH_3]^{2+}$
$B$. $[Ni(H_2O)_4(NH_3)_2]^{2+}$ and
$C$. $[Ni(H_2O)_3(NH_3)_3]^{2+}$ is