When two ice cubes are pressed together and join to form one cube, the force responsible for holding them together is hydrogen bond formation.

Hydrogen bond formation is a type of intermolecular force that occurs between a hydrogen atom bonded to an electronegative atom (such as oxygen or nitrogen) and another electronegative atom in a different molecule. In the case of ice, the hydrogen bonds form between the oxygen atoms of one ice cube and the hydrogen atoms of the other ice cube.

Vander Waals forces, on the other hand, are weaker intermolecular forces that arise from temporary fluctuations in electron distribution within molecules. They are not the primary force holding together the ice cubes.

Covalent attraction is a bond formed by the sharing of electrons between atoms in a molecule, and it is not relevant in this context.

Dipole interactions occur when there is a partial positive and partial negative charge in different molecules. While dipole interactions can play a role in the overall interaction between ice cubes, they are not specifically responsible for holding the ice cubes together.

In conclusion, the correct answer is hydrogen bond formation.