Using a cathode ray tube, thomson confirmed that

electron exists

Each metal emits cathode rays. J.J. Thomson used small cathode ray tube in his experiment. On the side of the tube, cathode rays were produced which were passed through the anode. Thereafter, magnetic field was applied across the cathode ray tube using a magnet. He noted that the cathode rays were deflected by the magnet. The path of cathode rays was detected using fluorescence on a screen. The deflection of the path was independent of the material of the anode and the gas in the jar and dependent on just the material of cathode. In the absence of magnet, electrometer detected negative charge. This negative charge was associated with the ray itself and could not be separated.  

This negative charge is possessed by electrons, the subatomic particle.

28. evolution

29. environment, survive, offspring  

explanation: