ln the Lewis structure of nitrous acid :

 

 

What is the formal charge on nitrogen?

 

Formal Charge = [valence electrons on atom] -  [number of bonds+ non-bonded electrons].

since, in HNO₂  center atom is nitrogen . Here, HNO₂  structure has  '1' C=O bond, '1' C-O bond and '1' O-H 

Therefore,

formal charge of N = 0.

Hence Correct option is B.