Among the following,the species that is both tetrahedral and diamagnetic is:

Match List-$I$ with List-$II$.

List-$I$ (Complex)	List-$II$ (Hybridisation of central metal ion)
$A$. $[CoF_6]^{3-}$	$I$. $d^2sp^3$
$B$. $[NiCl_4]^{2-}$	$II$. $sp^3$
$C$. $[Co(NH_3)_6]^{3+}$	$III$. $sp^3d^2$
$D$. $[Ni(CN)_4]^{2-}$	$IV$. $dsp^2$

Choose the correct answer from the options given below:

Which of the following compounds has a tetrahedral geometry?

Number of identical $Cr-O$ bonds in dichromate ion $Cr_2O_7^{2-}$ is

The structure of iron pentacarbonyl,$Fe(CO)_5$,is ................. .

Consider the following test for a group-$IV$ cation.
$M^{2+} + H_2S \rightarrow A$ (Black precipitate) $+$ byproduct
$A + \text{aqua regia} \rightarrow B + NOCl + S + H_2O$
$B + KNO_2 + CH_3COOH \rightarrow C + \text{byproduct}$
The spin only magnetic moment value of the metal complex $C$ is $BM$. (Nearest integer)