The correct option is C Both A & B
Gunpowder is a mixture of sulphur, charcoal and potassium nitrate (nitre). Amongst these, potassium nitrate (saltpeter) is a major constituent of gun powder.
The following reactions takes place on ignition-
2KNO3(s)+2S(s)→K2SO4(s)+SO2(g)+N2(g)
2KNO3(s)+4C(s)→K2CO3(s)+3CO(g)+N2(g)