The average kinetic energy of water molecules is directly related to the temperature of the water. Therefore, to order the samples from greatest to least average kinetic energy, we will arrange them based on their temperatures:
- Sample M: 88
- Sample L: 40
- Sample N: 21
Now, putting them in order from greatest to least temperature (and thus greatest to least average kinetic energy):
- M (88)
- L (40)
- N (21)
So the correct order is: M, L, N.