Answer - Potassium chlorate
Explanation-
Composition of oxygen potassium and chlorine makes a salt named potassium chlorate. It finds its use in many areas like disinfectant oxidizing agents explosives etc.
[tex]KClO_{3}[/tex] or potassium Chlorate has a low solubility in water hence among all other salts at 20 degree centigrade this one has the least chances of dissolving in it.
Since increase in temperatures are responsible for increase in solubility of many others it also happens with [tex]KClO_{3}[/tex] but compared to others even increase temperature solubility is lesser from others.
