Which of the following is a true statement?

Assign $A, B, C, D$ from the given type of reaction.
$NO + NO_2 \xrightarrow{-11 \ ^{\circ}C} N_2O_3$

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

Which of the following will not change the orange colour of $K_2Cr_2O_7$ into green colour in an acidic medium?

Assign $A$,$B$,$C$,$D$ from the given type of reaction.
$Na_2CO_3 + Pb(NO_3)_2 \longrightarrow PbCO_3 \downarrow + 2NaNO_3$

Which of the following reactions will lead to a redox reaction?