Nitrogen gas is obtained by thermal decomposition of .... .

Which of the following statements are correct?
$(I)$ $P_4$ molecule is very reactive because of angular strain.
$(II)$ The basicity of $H_3PO_3$ is $3$.
$(III)$ In gas phase,all $P-Cl$ bonds of $PCl_5$ have same bond length.
$(IV)$ In solid state,$PCl_5$ exists as an ionic solid,in which anion $[PCl_6]^-$ has octahedral and cation $[PCl_4]^+$ has tetrahedral shape.

Assertion $:$ Reducing nature of pnicogen hydrides increases on moving down the group.
Reason $:$ Thermal stability of pnicogen hydrides decreases on moving down the group.

Name three oxoacids of nitrogen. Write the disproportionation reaction of that oxoacid of nitrogen in which nitrogen is in $(+3)$ oxidation state.

The number of $H$ atoms attached to the phosphorus atom in hypophosphorous acid is

Given below are two statements:
Statement $I$: The halogen that makes the longest bond with hydrogen in $HX$ has the smallest covalent radius in its group.
Statement $II$: $A$ group $15$ element's hydride $EH_3$ has the lowest boiling point among corresponding hydrides of other group $15$ elements. The maximum covalency of that element $E$ is $4$.
In the light of the above statements, choose the correct answer from the options given below.