See explanation below.
Work Step by Step
Intermolecular forces are caused by the attraction of dipoles (partial charges) of molecules. This would be a "between molecules" attraction. The strongest intermolecular force is Hydrogen bonds (which aren't technically "bonds", this can be misleading). This one is caused by the + charge of Hydrogen in a molecules and an electronegative atom ( N, F, O) in another molecule. London forces are the weakest and that's because they're caused by molecules that have temporary dipoles. Covalent bonding however, requires the sharing of electrons, this is what "bonds" them therefore, it requires much more energy to break, since the particles have a strong hold on electrons. Covalent bonding is an intramolecular force, meaning "within a molecule" not between molecules, these are always stronger.