d. the average kinetic energy of the molecules in a substance.
Explanation:Note that:
• Temperature is the degree of hotness of coldness of an object
,• It is the measure of the average kinetic energy possessed by the molecules of a substance
,• The kinetic energy possess by the molecules of a substance increases when the substance is heated
Therefore, with the points highlighted above, the temperature of a substance is determined by the average kinetic energy of the molecules in a substance.