The correct option is A 1
For a compound with molecular formula CcHhXxNnOo
Degree of unsaturation=(c+1)−h2−x2+n2
Where, X = Halogen
c = number of carbon atoms
h = number of hydrogen atoms
n = number of nitrogen atoms
o = number of oxygen atoms
In C4H9ON:
Degree of unsaturation=(4+1)−92+12=1