The correct answer is option D, that is, positive.
The model of Thomson was overturned by Rutherford in 1911 with the help of gold-foil experiment in which he described that the atom possesses a heavy and tiny nucleus. He designed an experiment to use the alpha particles discharged by a radioactive element. In the experiment, the majority of the beams passed through the foil, however, some of them got reflected.
Thus a conclusion was made that a majority of the positive charge of an atom is concentrated in a comparatively tiny space at the middle of the atom, which is known at present as the nucleus. This concentrated central charge and mass are accountable for the deflection of alpha particles.