$KI$ is oxidised into $I_2$ by using the reagent

Assign $A, B, C, D$ from the given type of reaction.
$CaSO_4 + Pb(NO_3)_2 \longrightarrow PbSO_4 \downarrow + Ca(NO_3)_2$

What is obtained when solutions of $KI$ and $CuSO_4$ are mixed?

If zinc pieces are added to yellow $FeCl_3$ solution,it turns to very light green. It is because

The following reaction describes the rusting of iron:
$4Fe + 3O_2 \to 4Fe^{3+} + 6O^{2-}$
Which one of the following statements is incorrect?

How do you account for the following observations?
$(a)$ Though alkaline potassium permanganate and acidic potassium permanganate both are used as oxidants,yet in the manufacture of benzoic acid from toluene,we use alcoholic potassium permanganate as an oxidant. Why? Write a balanced redox equation for the reaction.
$(b)$ When concentrated sulphuric acid is added to an inorganic mixture containing chloride,we get a colourless pungent-smelling gas $HCl$,but if the mixture contains bromide,then we get red vapour of bromine. Why?