In $Kjeldahl’s$ method,$CuSO_4$ acts as

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

List-$I$ (Functional group detection)	List-$II$ (Change observed during detection)
$A$. Unsaturation (Baeyer's test)	$I$. Red colour appears
$B$. Alcoholic group (Ceric ammonium nitrate test)	$II$. Silver mirror appears
$C$. Aldehyde group (Tollen's reagent)	$III$. Violet colour appears
$D$. Phenolic group ($FeCl_3$ test)	$IV$. Discharge of pink colour

Choose the correct answer from the options given below:

Discuss the chemistry of Lassaigne's test.

Appearance of blood red colour,on treatment of the sodium fusion extract of an organic compound with $FeSO_4$ in presence of concentrated $H_2SO_4$ indicates the presence of element/s

Which of the following compounds will give a positive Lassaigne's test for both nitrogen and halogen?

Given below are two statements :
Statement $I$ : Nitrogen,sulphur,halogen and phosphorus present in an organic compound are detected by Lassaigne's Test.
Statement $II$ : The elements present in the compound are converted from covalent form into ionic form by fusing the compound with Magnesium in Lassaigne's test.
In the light of the above statements,choose the correct answer from the options given below :