When electric field is applied, cathode rays bend towards:
$A)$Negative plate
$B)$positive plate
$C)$Will remain unaffected in electric field
$D)$Cannot predict

Hint: A cathode ray tube consists of a sealed glass tube fitted at both ends with metal disks called electrodes. The electrodes are then connected to a source of electricity. One electrode, called the anode, becomes positively charged while the other electrode, called the cathode, becomes negatively charged.

Complete answer:
Cathode rays are streams of electrons observed in discharge tubes. If an evacuated glass tube is equipped with two electrodes and a voltage is applied, glass behind the positive electrode is observed to glow, due to electrons emitted from the cathode the electrode connected to the negative terminal of the voltage supply.
At the point when cathode rays are exposed to an electrical field, these get redirected towards the positively charged plate. The cathode rays accelerate vertically downwards under the influence of the constant downward force downwards on them due to the electric field produced by the charged plates.
Charged body would draw in just a contrarily charged body, consequently the particles of cathode beams convey negative charge. The cathode rays move at constant speed horizontally but faster and faster towards the positively charged plate
So, the correct answer is $B)$.

Note:
Cathode rays are undetectable, yet this incidental fluorescence permitted specialists to see that objects in the cylinder before the cathode, like the anode, cast sharp-edged shadows on the shining back divider. German physicist Johann Hittorf was first to understand that something should go in straight lines from the cathode to project the shadows.