The number of hydrogen atoms directly attached to the phosphorus atom in phosphorous acid is

What is the lowest oxidation state possessed by phosphorus in its oxyacids?

Phosphorus pentachloride in the solid state exists as:

In the Ostwald process for the manufacture of $HNO_3$,which of the following is used as a catalyst?

Based on the compounds of group $15$ elements,the correct statement$(s)$ is (are):
$(A)$ $Bi_2O_5$ is more basic than $N_2O_5$
$(B)$ $NF_3$ is more covalent than $BiF_3$
$(C)$ $PH_3$ boils at a lower temperature than $NH_3$
$(D)$ The $N-N$ single bond is stronger than the $P-P$ single bond

Which blue liquid is obtained on reacting equimolar amounts of two gases at $-30\,^oC$?