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					 In a discharge tube ionization of enclosed gas is produced due to collisions between
 
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- negative electrons and neutral atoms /molecules 
 - photons and neutral atoms /molecules 
 - neutral gas atoms/molecules 
 - positive ions and neutral atoms/molecules
 
 
Correct Option: A
When electrons emitted from cathode collide with gas molecules or atoms, they knock out outer electrons and produce positively charged ions. They become part of positive rays.