Identify the last step in wet chemical synthesis of nanomaterial.

What is a fusion mixture?

Identify the type of precipitate formed in the following reaction: $(NH_4)_2SO_4 + Ba(OH)_2 \longrightarrow BaSO_4 \downarrow + 2NH_3 \uparrow$

On performing a borax-bead test with a given inorganic mixture for qualitative analysis,the colour of the bead was found to be emerald green both in oxidising and reducing flame. It indicates the possibility of the presence of

Which of the following salts does not give a borax bead test?

Assign $A, B, C, D$ from the given type of reaction.
$MCrO_4 \downarrow (M^{2+} = Ba^{2+}, Pb^{2+}) + AcOH \longrightarrow$ No dissolution