Correct option is (a) AgNO3
AgNO3 is silver nitrate, which is a soluble salt in water.
On strong heating, AgNO3 decomposes to give out oxygen gas, leaving behind silver metal as the residue.
The reaction can be represented as: AgNO3(s) → Ag(s) + NO2(g) + 1/2O2(g)
The nitrogen dioxide gas is brown in color, and the oxygen gas can support combustion.
Silver metal is not highly reactive and remains as a residue.
Therefore, on strong heating, the nitrate which leaves behind the metal as the residue is AgNO3.
