Which one of the following correctly defines 1 K, as per the internationally accepted definition of temperature scale?
a. 1/100th of the difference between normal boiling point and normal freezing point of water
b. 1/273. 15th of the normal freezing point of water
c. 100 times the difference between the triple point of water and the normal freezing point of water
d. 1/273. 15th of the triple point of water