Cathode rays are passing through a discharge tube, in tube, there is

We know that cathode rays constitute a stream of electrons which are responsible for thermionic emission. Therefore, field will be created hence option D should be ruled out. We know it is due to charge magnetic field is created. We also know that magnetic field and electric field complement each other. Magnetic and electric field concepts are relative to each other, that it depends on which frame of reference you are taking about hence both fields are created inside tube

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