When $CuSO_4$ reacts with $KI$,the oxidation number of $Cu$ changes by

Assign $A$,$B$,$C$,$D$ from the given type of reaction.
$BaCO_3 \downarrow + 2CH_3COOH \longrightarrow Ba(CH_3COO)_2 + CO_2 \uparrow + H_2O$

Given below are two statements:
Statement-$I$ : Heating $NaCl$ with concentrated $H_2SO_4$ and $MnO_2$ results in oxidation of $Mn$.
Statement-$II$ : Heating $NaI$ with concentrated $H_2SO_4$ and $MnO_2$ results in reduction of $Mn$.
In light of the above statements, choose the most appropriate answer from the options given below:

Assign $A$,$B$,$C$,$D$ from the given type of reaction.
$MnS(s) + 2HCl(aq) \longrightarrow MnCl_2(aq) + H_2S(g)$

Which of the following options are correct for the reaction
$2[Au(CN)_2]_{(aq)}^{-} + Zn_{(s)} \rightarrow 2Au_{(s)} + [Zn(CN)_4]_{(aq)}^{2-}$
$A.$ Redox reaction
$B.$ Displacement reaction
$C.$ Decomposition reaction
$D.$ Combination reaction
Choose the correct answer from the options given below:

Assign $A$,$B$,$C$,$D$ from the given type of reaction.
$FeSO_4 + Na_2S \longrightarrow FeS \downarrow$