No, the correct answer is d) light exhibits wave-particle duality.
To arrive at this answer, we can eliminate options a), b), and c) as they are not specific to Planck's contributions to the quantum theory of the atom.
Option a) refers to Einstein's famous equation E=mc^2, which describes the relationship between mass and energy but was not proposed by Planck.
Option b) refers to Heisenberg's uncertainty principle, which states that the more precisely we know the position of a particle, the less precisely we can know its momentum, and vice versa. This principle was also not proposed by Planck.
Option c) refers to the wave-particle duality of matter, which was introduced later by de Broglie, stating that particles like electrons can exhibit wave-like characteristics. Again, this was not Planck's contribution.
Option d), on the other hand, correctly identifies Planck's contribution to the quantum theory of the atom. In 1900, Planck proposed that light (electromagnetic radiation) consists of discrete packets of energy called quanta or photons. This idea revolutionized our understanding of light and laid the foundation for the development of quantum mechanics.