Match the terms in Column-I with their description in Column-II:
Column-I Column-II (P) N2O5 (i) N–N bond (Q) N2O (ii) N–O–N bond (R) N2O4 (iii) N=N / NN bond (S) NO2 (iv) N=O bond
P – (ii), Q – (iii), R – (i), S – (iv)
The number of oxygen atoms present in chemical formula of fuming sulphuric acid is _______.