Question

2 in the late 1800s, experiments using cathode ray tubes led to the discovery of the --
options: proton, positron, electron, neutron

Explanation:

In the late 1800s, J.J. Thomson conducted experiments with cathode ray tubes. These experiments showed that cathode rays were composed of negatively charged particles, which were later named electrons. Protons were discovered later by Rutherford, positrons are antimatter counterparts of electrons discovered much later, and neutrons were discovered by Chadwick. So the discovery from cathode ray tube experiments was the electron.

Answer:

C. electron