The correct option is B 0.2
9.2 g of N2O4(g) corresponds to 9.292=0.1 moles
Out of these 0.05 moles (50% of 0.1 moles) dissociate to form 2×0.05=0.1 moles of NO2(g)
The equilibrium constant is Kc=[NO2]2N2O4=(0.1)20.05=0.2
Hence the correct option is B.