$Fe^{3+}$ is reduced to $Fe^{2+}$ by using:
$A$. $H_2O_2$ in presence of $NaOH$
$B$. $Na_2O_2$ in water
$C$. $H_2O_2$ in presence of $H_2SO_4$
$D$. $Na_2O_2$ in presence of $H_2SO_4$

Justify that the following reactions are redox reactions:
$(a) \ CuO_{(s)} + H_{2(g)} \to Cu_{(s)} + H_2O_{(g)}$
$(b) \ Fe_2O_{3(s)} + 3CO_{(g)} \to 2Fe_{(s)} + 3CO_{2(g)}$
$(c) \ 4BCl_{3(g)} + 3LiAlH_{4(s)} \to 2B_2H_{6(g)} + 3LiCl_{(s)} + 3AlCl_{3(s)}$
$(d) \ 2K_{(s)} + F_{2(g)} \to 2K^+F^-_{(s)}$
$(e) \ 4NH_{3(g)} + 5O_{2(g)} \to 4NO_{(g)} + 6H_2O_{(g)}$

Assign $A, B, C, D$ from given type of reaction.
$2KI + CuSO_4 \longrightarrow CuI \downarrow + \frac{1}{2}I_2 + K_2SO_4$

In the reaction between moist $SO_2$ and acidified permanganate solution:

Which of the following species is both basic and a reducing agent?

$HNO_2$ acts as