The most stable resonance structure I came across this question:


  Which is the most stable resonating structure of p-nitrosobenzene
  among the following?
  
  


I have been taught about the priorities for resonance structure stability as follows:


  
  Complete octet $\rightarrow$ more stable
  Uncharged $\rightarrow$ more stable
  Lower formal charge $\rightarrow$ more stable
  Less separation between opposite charges $\rightarrow$ more stable 
  Negative charge near more electronegative atoms and positive charge near less electronegative atoms $\rightarrow$ more stable 
  


So according to the above rules, (b) and (c) are the among the most stable. Bu then applying rule #4 above, (b) should be more stable, because here each positive charge is in vicinity of negative charge.

However the answer given is (c). Why is this?
Because on C; the negative charge should be on oxygen (the more electronegative element) instead of on carbon