Which one of the following salts gives a green-coloured flame when the salt is tested by a $Pt$ wire?

$A$ chemistry student trying to detect the metallic ion in a salt,makes a paste on a clean platinum wire loop of the salt with concentrated $HCl$. When he takes a small amount of this paste and keeps it in a non-luminous Bunsen flame,the colour of the flame changes to grassy green. He should,therefore,conclude that the metal is

Match List-$I$ with List-$II$ and choose the correct answer from the options given below:

List-$I$ (Name of the test)	List-$II$ (Reaction sequence involved) [$M$ is metal]
$A$. Borax bead test	$I$. $MCO_3$ $\rightarrow MO$ $\xrightarrow[+\Delta]{Co(NO_3)_2} CoO \cdot MO$
$B$. Charcoal cavity test	$II$. $MCO_3$ $\rightarrow MCl_2$ $\rightarrow M^{2+}$
$C$. Cobalt nitrate test	$III$. $MSO_4$ $\xrightarrow[\Delta]{Na_2B_4O_7} M(BO_2)_2$ $\rightarrow MBO_2$ $\rightarrow M$
$D$. Flame test	$IV$. $MSO_4$ $\xrightarrow[\Delta]{Na_2CO_3} MCO_3$ $\rightarrow MO$ $\rightarrow M$

In the flame test of a mixture of salts,a green flame with a blue centre was observed. Which one of the following cations may be present?

Which of the following salts is used in the bead test for the qualitative analysis of inorganic substances?

When sodium chloride is heated with concentrated $H_2SO_4$ and solid potassium dichromate,which compound containing $Cr$ in the $+6$ oxidation state is formed as a gas?