$(NH_4)_2Cr_2O_7$ on heating gives:

$NH_3$ gas is not liberated by which of the following combinations?

Cyanogen gas is obtained in the reaction:

By the action of hot conc. $H_2SO_4,$ phosphorus changes to

Find the correct statements related to group $15$ hydrides.
$A$. Reducing nature increases from $NH_3$ to $BiH_3$
$B$. Tendency to donate lone pair of electrons decreases from $NH_3$ to $BiH_3$
$C$. The stability of hydrides decreases from $NH_3$ to $BiH_3$
$D$. $HEH$ bond angle decreases from $NH_3$ to $SbH_3$ ($E$ = Elements of group $15$)
Choose the correct answer from the options given below:

Bones glow in the dark because