A colourless water-soluble compound on strong heating liberates a brown colored gas and leaves a yellow residue that turns white on cooling. An aqueous solution of the original solid gives a white precipitate with `(NH_(4))_(2)S`. The original solid is :
A. `Zn(NO_(3))_(2)`
B. `Ca(NO_(3))_(2)`
C. `Al(NO_(3))_(3)`
D. `NaNO_(3)`
