Match the gases in List I with the observation in List II. List I: (i) $\mathrm{CO}{}_2$; (ii) $\mathrm{SO}{}_2$; (iii) $\mathrm{H}{}_2\mathrm{S}$; (iv) $\mathrm{NO}{}_2$. List II: (p) rotten-egg odour, blackens lead acetate paper; (q) reddish brown gas, turns moist starch-iodide paper blue; (r) colourless pungent gas, turns acidified dichromate paper green, does not blacken lead acetate paper; (s) odourless, turns lime water milky, no effect on acidified dichromate paper.

1. A(i)-(s), (ii)-(r), (iii)-(q), (iv)-(p)
2. B(i)-(r), (ii)-(s), (iii)-(p), (iv)-(q)
3. C(i)-(s), (ii)-(r), (iii)-(p), (iv)-(q)
4. D(i)-(s), (ii)-(p), (iii)-(r), (iv)-(q)