Technically metals get expansions due to heat in dimensions because of the energies of 

Explanation:-

• Metals expand in dimensions when heated due to the increased vibrational energy of the atoms within the metal.
• This increase in vibrational energy causes the atoms to move more vigorously and occupy a greater average distance, leading to thermal expansion.

This vibrational energy can be described in terms of phonons, which are quantized modes of vibrations of the crystal lattice.

• Phonons: Phonons represent the vibrational energy of atoms in the solid's lattice. Increased phonon energy with temperature leads to greater atomic vibrations and thus expansion.
• Heat: Heat is the transfer of thermal energy which raises the temperature, but it is the resultant phonon energy that directly causes expansion.
• Electrons: While electrons contribute to thermal conductivity, they are not the primary factor in thermal expansion.
• Photons: Photons are involved in radiative heat transfer rather than the mechanical expansion of a solid.

Given these explanations, the correct answer is phonons