what does addition of potassium nitrate to ice results in??why and how?

a)increase in melting point

b)decrease in melting point

c)change in colour of ice

d)both (a) &(b)

(please give the answer with explaination)

Option B is the correction answer because depression in freezing point depends upon the number of atom, ion or molecules present in the solution which decreases the polarity between solvent molecules.  For example: Addition of NaCl to water decreases its freezing point to -9°C i.e. at this temperature water will melt also.