The following compounds are heated, (i) $$\mathrm{KNO_3}$$, (ii) $$\mathrm{Cu(NO_3)_2}$$, (iii) $$\mathrm{Pb(NO_3)_2}$$, (iv) $$\mathrm{NH_4NO_3}$$. Which of the following statements is correct?

A

(ii) and (iii) liberate $$\mathrm{NO_2}$$

B

(iv) liberates $$\mathrm{N_2O}$$

C

(i), (ii) and (iii) liberate $$\mathrm{O_2}$$

D

All statements are correct