Jack researched J. J. Thomson’s experiments. Read Jack’s summary below and find the error.

Thomson made a beam, called a gamma ray, travel out of a metal plate and through a tube. He placed electrically charged plates outside the tube and saw that this deflected the beam. This meant the beam was electrically charged. The fact that metals could produce electrically charged particles meant that the atom could be divided.
a. Error is in sentence 2. He placed magnetically charged plates outside the tube.
b. Error is in sentence 4. The production of electrically charged particles showed that the atom could not be divided.
c. Error is in sentence 2. The beam was not deflected.
d. Error is in sentence 1. The beam was a cathode ray.