The correct option is D 2k1[NO2]2+k2[NO2][SO2]
For the reaction 2NO2k1→N2O4 and NO2+SO2k2→NO+SO3, the rate of the reaction is −12d[NO2]dt=k1[NO2]2.
⟹ −d[NO2]dt=2k1[NO2]2 .....(1)
For the reaction 2NO2k1→N2O4 and NO2+SO2k2→NO+SO3, the rate of the reaction is −d[NO2]dt=k2[NO2][SO2] ......(2)
So, from equations (1) and (2), we get the rate of disappearance of NO2 is equal to −d[NO2]dt=2k1[NO2]2+k2[NO2][SO2].