Respuesta :
London dispersion is present, as we can see C3H5(OH)3 is very branched, when a molecule is branched it has a low boiling point due to how compact the surface area is compare to C3H7OH which has a large surface area (in this molecule there is only on branch)

Answer:
From lowest to highest boiling point, we would have;
C3H7OH < C3H6(OH)2 < C3H5(OH)3
Explanation:
Considering the three compounds in question, there is just one type of inter-molecular force that differentiates them and that is the Hydrogen bond. This dipole-dipole bond exists between a hydrogen molecule and an electronegative molecule (oxygen in this case -OH).
There is just one of such bond/force in the first compound, two in the second and three in the last one. The more the hydrogen bond, the more the inter-molecular forces present in the compounds and the higher the boiling point. Thus we have in terms of boiling point;
C3H7OH < C3H6(OH)2 < C3H5(OH)3