Which of the following statement(s) is/are correct regarding the different atom models? 

This is a multiple-correct question, and the correct options are (b), (c) and (d). Thomson pictured the atom as a uniform sphere of positive charge and mass with electrons embedded in it. Bohr's model allows electrons only in certain stationary circular orbits ($$n = 1, 2, 3, \ldots$$), of which there are many. Most $$\alpha$$-particles passed undeflected in Rutherford's experiment, showing that the atom is mostly empty, whereas the mass of the $$\alpha$$-particle was not established by his model.