From his experiments, j. j. thomson concluded that
a. cathode ray particles can move at very fast speeds.
b. cathode ray particles can be moved by electric current.
c. atoms contain small positively charged particles that are called protons.
d. atoms contain small negatively charged particles that are called electrons

option D. Atoms containd small negatively charged particles that are called electrons.

JJ Thompson carried out three important experiments with cathode rays. With them he proveed that cathode rays were negative charged particles and that the ratio charge/mass was so large that the particles either had a huge charge or had a very small mass, and he came up with the latter, defining that these negative charged particle were very small.

Electrons are emitted

Remember that rust prevented by placing a sacrificial electrode in electrical contact with the iron. the sacrificial electrode must be composed of a metal that  oxidizes  more easily than iron (that is, it must be below iron in table 18.1).