Which is the best conductor of electricity .. 1.potassium chloride 2,water.3.sugar. 4 acetic acid?

So what are you talking about? Potassium chloride and sugar are solids. Potassium chloride is an excellent conductor when it melts. Acetic acid is a liquid, but conductivity is not mentioned at all among its properties. When it is dissolved in water, the solution is a good conductor. Water is a poor conductor in most situations. So it depends on what you are talking about and what you mean by "best".