Which of the following is the most stable resonance structure

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Explanation

Structure `(c ) ` is the most stabel resonance structure (i) Number of covalent bonds in (a) and (b) `=3`
(ii) Number of covalent bonds in (c ) and (d) `=14`
(iii) In ( c) Positive charge is no`N` whereas in (d) it is than `O` atom Since `N` uis less `EN` (electronegative) than `O` (c) is more stable
(iv) Order of stability `c gt d gt a gt b` .