Iodine on reaction with concentrated nitric acid forms:

1. HOI

2. HI

3. HIO₃

4. HIO₄

Among the following reactions,  N₂ is not generated by heating:

1. (NH₄)₂Cr₂O₇

2. NH₄Cl + NaNO₂

3. NH₄Cl + CaO

4. Ba(N₃)₂

Oxidation of nitrogen among the following reactions is indicated by -
1. $\mathrm{N}_2 \rightarrow 2 \mathrm{NH}_3$
2. $\mathrm{N}_2 \mathrm{O}_4 \rightarrow 2 \mathrm{NO}_2$
3. $\mathrm{NO}_3{ }^{-} \rightarrow \mathrm{N}_2 \mathrm{O}_5$
4. $\mathrm{NO}_2^{-} \rightarrow \mathrm{NO}_3^{-}$

NO₂ is the anhydride of

1. HNO₃

2. HNO₂

3. HNO₃ + HNO₂

4. None of the above 

$\mathrm{PCl}_3$ upon hydrolysis gives an oxyacid of phosphorous.
The basicity of that oxyacid is: