Which one of the following is correct with respect to basic character?

How is red phosphorus obtained from white phosphorus?

Among the members of $V$ $A$ group ($N$,$P$,$As$,$Sb$,and $Bi$),which of the following properties shows an increase as we go down from nitrogen to bismuth?

Which one of the following combines with $Fe(II)$ ions to form a brown complex?

Which of the following oxides of nitrogen is a mixed anhydride of two acids?

$A$ nitrogen oxide that forms "in situ" when dilute $FeSO_4$ is treated with an aqueous solution of nitrate ion and then carefully adding conc. $H_2SO_4$ along the sides of the test tube, is