Answer: Option (D) is the correct answer.
Step-by-step explanation:
An atom consists of three subatomic particles, that is, protons, neutrons and electrons.
Protons and neutrons reside inside the nucleus of an atom whereas electrons revolve around the nucleus of the atom.
According to Bohr, mass of an atom is concentrated inside the nucleus due to the number of protons and neutrons.On the other hand, electrons move in circular motion around the nucleus of an atom.
Hence, we can conclude that electrons are modeled using a “cloud”around the nucleus because they move in an orbit about the nucleus.