Compound A reacts with $NH _4 Cl$ and forms a compound B.
Compound B reacts with $H _2 O$ and excess of $CO _2$ to form compound $C$ which on passing through or reaction with saturated $NaCl$ solution forms sodium hydrogen carbonate Compound $A , B$ and $C$, are respectively.
The number of oxygen atoms present in chemical formula of fuming sulphuric acid is _______.
Match List I with List II
Choose the correct answer from the options given below: