Hi Pistolpete007. I believe that C10H20 has the highest entropy. Entropy is a measure of the disorder of the system. Since C10H20 contains the highest amount of molecules, then it would give off more disorder. Imagine a candy bag full of 10 candies, and one with 100, well it would take longer to cleanup the one with 100 candies because it creates a bigger mess. I am basing my answer on the number of atoms present since the compounds you gave do not have states (solid, liquid, gas, aq).
And yes, dleodyddlek, you are right that the smaller the molecule, less dispersion forces, and the lower the boiling point. But please note that this does not correlate with entropy, as entropy is again a measure of the amount of disorder pertaining to a system.
Have a good one.