Answer
d. Thomson
Step-by-step explanation
The given model shown above is Thomson's model of an atom.
In 1898, J. J. Thomson proposed that an atom is shaped like a sphere with a radius of approximately 10⁻¹⁰m, where the positive charge is uniformly distributed as shown in the model given. The electrons are embedded in this sphere so as to give the most stable electrostatic arrangement.
Thus, Thomson's model of an atom is also referred to as the watermelon model, the plum pudding model or the raisin pudding model.
An important aspect of Thomson's model of an atom is that it assumes that the mass of the atom is uniformly distributed over the atom. The model was successful in explaining the overall neutrality of the atom.