Right answer is (c) +3
Explanation: Di-nitrogen trioxide is formulated as N2O3
The oxidation state of oxygen atom is fixed at -2 since it is the more electronegative atom in this case.
If oxidation state of nitrogen is assumed to be ‘x’, then:
2x + (3x -2) = 0
2x – 6 = 0
x = +3
The oxidation state of nitrogen is +3.