D. There is a dense, positively charged mass in the center of an atom
<h2>Explanation:</h2>
Rutherford gave the idea that there is a dense part resent in the center of an atom which he named as a nucleus. When he shot a beam of alpha particles at a sheet of gold foil, a few particles were deflected. By this experiment he concluded that a tiny, dense nucleus was causing the deflections inside the center of an atom. He also concluded that most of the space inside the atom is empty because most of the α-particles passed through the gold foil passed through it without getting deflected.
A transitional topic sentence is most often implied, although of course it should be noted that this is not always the case, and that it varies greatly with the speaker.
