Which of the following compounds liberate ${\mathrm{N}}_2$ on heating?

${\left({\mathrm{NH}}_4\right)}_2{\mathrm{Cr}}_2{\mathrm{O}}_7$ compounds liberate ${\mathrm{N}}_2$ on heating

Ammonium dichromate breaks down when heated, releasing nitrogen gas and water vapour (gaseous owing to the reaction's temperature), as well as an orange spark and solid chromium(III) oxide that is green in colour. This reaction produces nitrogen gas.

Hence option A is correct