Answer: The correct answer is positive particles.
Step-by-step explanation:
Rutherford gave an experiment known as gold foil experiment.
In his experiment, he took a gold foil and bombarded it with alpha particles (carrying positive charge). He thought that the particles will pass straight through the foil, but to his surprise, many of them passed through, some of them deflected their path and a few of them bounced back.
From this he concluded that in an atom, there exist a small positive charge in the center. Due to this positive charge, the alpha particles deflected their path and some of them bounced straight back their path.
Hence, the correct answer is positive particles.