Propane C3H8 is burned with air

Propane C3H8 is burned with air, and the combustion products consist of CO2, CO, H2O, O2, N2, OH, H2, and NO. The number of equilibrium constant relations needed to determine the equilibrium composition of the mixture is
(a) 1 (b) 2 (c) 3 (d) 4 (e) 5