For part C it wants the Lewis structure for ONF. I did the structure and there has to be a double bond somewhere in order for all 18 e- to be accounted for. But where would the double bond be? To the O or the F?
As a follow up question, how do you know that O is going to form a double bond with N and not F? Maybe I'm missing something obvious here but how do we determine which atom will form a double bond with the central atom?