The cathode rays are-

A.)A stream of electrons
B.)A stream of positive ions
C.)A stream of uncharged particles
D.)The same as canal rays

Hint: Cathode ray, electron stream from the negative electrode ( cathode), in a low-pressure gas discharge tube, or from hot filament in certain electron tubes, in an electron. Cathode rays centered on a strong target (anticathode) produce an X ray or a very high temperature (cathode ray furnace) based on a tiny point in a vacuum. If cathode rays hit those molecules used for covering a cathode plate, they allow light to be released from the molecules (and hence the screen).

Step By Step Answer:
When combined with electrical and magnetic deflection of a cathode ray, this effect results in the cathode ray-oscilloscope (CRT) to monitor variations and values of the alternating voltage and currents and the imaging tube of the TV and radar. This is due to the controlled deflections of the cathode ray.

Cathode rays are named as they are released in a vacuum tube by a negative electrode or cathode. We will first be isolated from cathode atoms to expel electrons into the tube. Throughout the early cold cathode vacuum tubing, the Crookes tubing, a strong electric potential of thousands of volts has been used to ionize the residual gas atoms in the conduit between the anode and the cathode. The positive ions had been propelled to the cathode by the magnetic force, and electrons kicked out of its surface as they interacted with it; these became the cathode rays.

Hence, option A is the correct option.

Note: The thermionic radiation of contemporary vacuum tubes allows the cathode from a thin filament, heating through it by a different electrical current. The accelerated heat flow of the filament takes the electrons to the evacuated area of the tube from the top of the filament.