Answer:
D. Scientists collided atoms of small mass together, observed reaction products with twice the mass of original atoms, and described this result as fusion.
Step-by-step explanation:
The early atomic theory was purposed by Dalton and said that the atoms are the smallest particle, so they were indivisible. Further theories refuted that theory, such as Rutherford's experiment, in which particles alpha was bombarded in a gold foil, and was noticed that some of then have deviated, most passed through, and a few deviated completed.
Rutherford purposed that the atom is an empty space, with a small nucleus in the middle, and electrons orbiting it. But, most recently, by bombarding atoms of small mass together (such as hydrogen), scientists observed that other atoms with the double mass were formed, which means that it is impossible to the atom to be indivisible because had happened a fusion.