Which of the following compounds is one of the constituents of gunpowder?

Potassium hydroxide is an inorganic compound with the formula KOH. Its common name is caustic potash. It has many industrial and niche applications. Most applications exploit its reactivity towards acids and its corrosive nature. Potassium iodide is an inorganic compound with the chemical formula KI. This white salt is the most commercially significant iodide compound. It is used to loosen and break up mucus in the airways.  Potassium nitrate is a natural solid source of nitrogen. Major uses of potassium nitrate are in fertilisers, rocket propellants and fireworks. It is one of the constituents of gunpowder. Potassium oxide is an important compound used in fertilisers, ceramics, glass and optics.