In the context of atomic theory, what did Robert Millikan determine about the electron from his oil-drop experiment?

• A. He determined the electron’s charge-to-mass ratio, $\frac{e}{m}$, using deflection by electric and magnetic fields.
• B. He measured the magnitude of the electron’s charge and showed it is quantized in integer multiples of a fundamental value.
• C. He discovered the electron and demonstrated that cathode rays are streams of negatively charged particles.
• D. He proposed that electrons occupy fixed circular orbits around the nucleus with quantized energies.

Answer: (B)